Climate Change, Abraham, and COP 27: A Resource for Teaching and Preaching

Climate Change, Abraham, and COP 27: A Resource for Teaching and Preaching

The commentaries below are from Eco Bible: Volume 1: An Ecological Commentary on Genesis and Exodus, by Rabbi Yonatan Neril and Rabbi Leo Dee (Interfaith Center for Sustainable Development, Jerusalem, 2020).

https://www.jewishecoseminars.com/eco-torah/

Palace on Fire

Genesis 12:1 – The Lord said to Abram, “Go forth from your native land and from your father’s house to the land that I will show you.”

The Midrash explains how Abram (whose name becomes Abraham) discovered God. It describes Abraham passing by a palace that is on fire. He wonders aloud, “Is it possible that the palace doesn’t have an owner? Who is the owner of this palace?” The owner hears him and says, “It is Me!”1

In the words of Rabbi Yosef Y. Jacobson: “Abraham’s bewilderment is clear. This sensitive human being gazes at a brilliantly structured universe, a splendid piece of art. He is overwhelmed by the grandeur of a sunset and by the miracle of childbirth; he marvels at the roaring ocean waves and at the silent, steady beat of the human heart. The world is indeed a palace. But the palace is in flames. The world is full of … pain.”2

Rabbi Jonathan Sacks explains that the question, “Is it possible that the palace doesn’t have an owner?” speaks to the responsibility of humanity to put out the fire that we have started. The palace is a metaphor for nature.3 Today with global warming, the world’s great rainforests and boreal forests are burning as never before.4 One could look at the planet and legitimately ask, “Who is in charge of this problem?” And God’s response may be to us, just as it was to Abraham, “Go forth,” or “Reach into yourself.” In other words, we all share responsibility for our common home.

Sustainable Coexistence – by Rabbi Tuvia Aronson5

Genesis 13:6 – So that the land could not support them staying together; for their possessions were so great that they could not remain together.

Abraham and Lot’s inability to coexist on one piece of land leaps out at us. In our era, when environmental issues such as population, food, and land distribution divide communities and nations, we can look to this text for guidance. Rabbi Samson Raphael Hirsch and Rabbi Naftali Zvi Yehuda Berlin explain this verse to show that divisiveness put an extra burden on the land and the people.6

It was not because they had too many herds or because there was insufficient pasture for both of them. If they had combined their herds into one household, the land would have been sufficient. But if two people cannot agree, separate tents are needed—boxes, crates, everything separate for each of the two parties. Had their personalities been compatible, there would have been no need for separate pastures. Only profits counted in Lot’s enterprise, while Abraham’s household gave attention to higher interests.

Abraham and Lot’s attitudes were incompatible, therefore they could not cooperate. This is why the verse stresses “together”—yachdav. Interestingly, the second-century translator Onkelos translates yachdav using the wording “as one,” connoting the need for a deep interconnection that ultimately enables living in harmony with the Land.7 The Abrahamic tradition demands that we make our personal and societal decisions based on both environmental and social considerations.

Religious environmental education stresses the importance of togetherness. Community gardens are flourishing,8 and consumer assisted farming projects are enhancing life in ways that promote both communal unity and harmony with nature.9 Intentional ecological communities are gaining momentum. Concern for the environment crosses denominational and philosophical divides. Working as one to take care of our precious resources is incredibly powerful.

Famine in Genesis

Genesis 12:10 – There was a famine in the land, and Abram went down to Egypt to sojourn there, for the famine was severe in the land.

The verse emphasizes that Abraham and his family had to migrate due to the famine. In the land of Israel, the crops that depend on rainfall, like wheat, barley, olives, and grapes, produce little or no grain or fruit during a drought. Fig trees, pomegranate trees, and vegetables that depend on more water produce even less. In a sustained drought, even the springs dry up, which prevents irrigation.

According to Rabbeinu Bachaya (Bachaya ben Asher ibn Halawa), citing the rabbis of the Talmud, there were ten famines from Adam to the end of Genesis.10 The Midrash states that the Torah explicitly mentions only three famines, one each during the lifetimes of Abraham, Isaac, and Jacob.11 These three famines occur in a period of about 200 years.12

Ten extreme famines occurred in the twentieth century. They killed over 70 million people, predominantly in China, the Soviet Union, and India, and also drove migration of millions more to new regions.13 This suggests an average of ten years between major world famines. While the immediate and deeper causes of famines are complex, unsustainable agricultural practices contributing to salinity, loss of natural water bodies, or soil erosion can play a role.14

A 2019 United Nations Climate Change report highlights the increased likelihood of future, major global famine due to climate change, stressing the world’s major breadbaskets.15 Abraham and Sarah had no choice but to become famine refugees. Today, the individual and collective actions of people could reduce the frequency and severity of famines in our times and in the future.

The Dead Sea Is Dying

Genesis 13:10 – Lot looked about him and saw how well watered was the whole plain of the Jordan, all of it—this was before the Lord had destroyed Sodom and Gomorrah—all the way to Zoar, like the garden of the Lord, like the land of Egypt.

In Biblical times, the Dead Sea region was lush and fertile, like the Garden of Eden. Ralbag (Rabbi Levi ben Gershon) explains that the Dead Sea valley had many fields, suggesting that there was ample water for irrigation at that time.16 Rashi teaches that it had streams, trees, and crops.17

Over the past sixty years, modern irrigation techniques have significantly expanded agriculture in Israel, Jordan, Syria, and Lebanon. In addition, many millions of people now live in the Dead Sea drainage basin. They use water for domestic and industrial uses, including the extraction of Dead Sea minerals. This has threatened the region’s ecology, with significant lowering of the Dead Sea’s water level and formation of sinkholes around the sea. The diversion of tributary rivers and streams for human use has significantly reduced the annual flow to the Dead Sea, just as climate change has made rainfall in the Dead Sea watershed scarcer.18 Dead Sea water levels continue to decline at a rate of about 3.4 feet (1.1 meter) per year.19 Without significant international action, the Dead Sea may suffer a similar fate as two of the world’s great lakes— Lake Baikal in Russia, and Lake Mali in Africa, which have shriveled in recent decades. That the Torah describes the Dead Sea valley as comparable to the Garden of Eden should motivate us to stop and reverse the damage we have already done.

Hiking the Land

Genesis 13:17 – Get up, walk about the land, through its length and its breadth, for I give it to you.

Abraham connected to God by being alone in nature. Abraham was commanded to walk the width and breadth of Israel. Why is this one of very few commands given to him? Abraham traveled throughout the Middle East by foot and by donkey—from present-day Iraq, crossing through Turkey, Syria, and Egypt, before returning to Israel. His travels and time in nature created a foundation for his spiritual growth and awareness. He also kept himself in good physical shape. At the age of 127, the Bible says, he hiked for three days and climbed Mount Moriah for the binding of Isaac.

Isaac also connected to God through nature when he went out into the fields. So did Jacob when he slept and dreamt of the ladder, alone outdoors. How many city dwellers today have ever slept alone in nature? How can we bridge the ecological gap between our lifestyle and that of our forefathers?

Stuck in Crude Oil

Genesis 14:10 – Now the Valley of Siddim was dotted with bitumen pits; and the kings of Sodom and Gomorrah, in their flight, threw themselves into them, while the rest escaped to the hill country.

The kings of Sodom and Gomorrah fell into pits of “black gold” or bitumen, also known as asphalt (in Hebrew chemar).20 In ancient times as today, surface seepages of this thick, sticky form of crude oil21 occurred and still occur in a limited number of places in the world, including Azerbaijan, Iran, Pennsylvania, Alberta, and the Dead Sea in Israel.22 People used and still usethe natural tar for its waterproofing qualities23 and for roads.

Why does the Torah mention this geological detail in relation to the leaders of these ultimately decimated societies? The Torah continues, “The invaders [four Middle Eastern kings] seized all the wealth of Sodom and Gomorrah and all their provisions, and went their way.”24 Once the kings fell into the bitumen pits, they got trapped and lost all of their wickedly gained wealth. The story of the kings stuck in bitumen relates deeply to our world today. Canada is the planet’s 4 oil producer, and 60 percent of its oil comes from the bitumen of oil sands.25

The Canadian province of Alberta has most of the world’s reserves of natural bitumen in the Athabasca oil sands, an area larger than England.26 Bitumen is considered the dirtiest and most polluting fossil fuel, due to the energy required to separate the crude oil from the sand.27 Today, we and our leaders are trapped by economic inertia and political resistance. Oil remains our fuel of choice to make gasoline for cars and trucks, jet fuel for airplanes, tar and asphalt for paving the roads, and even plastic which is filling our oceans with trash that never fully breaks down.

The Midrash teaches that Abraham, the prophet of light, pulled the kings out of the bitumen pits.28 Abraham provides an example of lifting people from being trapped in fossil fuels. In our times, scientists published a 2017 study and environmental roadmap on how most countries in the world could transition to 100 percent wind, water, and solar energy by 2050.29 We do not need to wait until someone rescues us—or until we run out of all fossil fuels—but can now take steps as individuals, communities, and nations to free ourselves from devastating fossil fuel use.

Abraham and Self-Satisfaction

Genesis 14:22-23 – But Abram said to the king of Sodom, “I swear to the Lord, God Most High, Creator of heaven and earth: I will not take so much as a thread or a sandal strap of what is yours; you shall not say, ‘It is I who made Abram rich.’”

Abraham recognizes where wealth and abundance ultimately come from—God. The Maharal of Prague (Judah Loew ben Bezalel) taught that Abraham epitomizes “satisfaction with what one has” and being content with what arrives in one’s hand based on a normal amount of work.30 Rashi points out that Abraham was sure to make his living through honest means, by only grazing his flocks on ownerless land.31 The trait of self-satisfaction flows from an awareness that God provides each person based on their merit. Abraham appreciates the gift of being fully alive through meeting his needs through his own efforts and has no need of gifts from the king of Sodom.

In modern consumer society, we would be wise to learn from Abraham. Being satisfied with what we have, instead of constantly seeking more things, is a root solution for ecological sustainability.

Finding God Outdoors

Genesis 15:5 – He took him outside and said, “Look toward heaven and count the stars, if you are able to count them.” And He added, “So shall your offspring be.”

Why did God take Abraham outside? Ibn Ezra writes poetically of finding God, “Wherever I turn my eyes, around on earth or to the heavens, I see You in the field of stars, I see You in the yield of the land, in every breath and sound, a blade of grass, a simple flower, an echo of Your holy Name.”32

Elie Wiesel relates: When the Holy Seer of Lublin was a little boy, he was known to skip school for hours or even days. Once, his teacher followed the young boy to see what became of these free moments. The Seer walked to the edge of the town, into deep woods, and there, in a small, green circle of trees, he began to pray. The next day the teacher asked the boy what drew him to those woods. The Seer of Lublin replied, “I can find God there.” “But,” said the teacher, “surely God is the same in the town as in the woods.“ “That’s true,” replied the Seer, “but I am not the same!”33

The Cure Before the Sickness

Genesis 15:13-14 – Know well that your offspring shall be strangers in a land not theirs, and they shall be enslaved and oppressed four hundred years; but I will execute judgment on the nation they shall serve, and in the end they shall go free with great wealth.

Rabbi Mordechai Hochman explains that these verses encapsulate the rabbinical dictum that “God gives us the cure before the sickness.” In other words, God tells Abraham that his descendants will suffer but emerge much stronger from it.34

With regard to sustainability, it is easy to think that the world is doomed to destruction. However, God has given us the cure before the sickness. There have never been so many possible solutions available for reducing carbon emissions (solar panels are cheaper than ever), for conserving water, and for replacing single-use plastics. Our challenge as humankind is in deciding to embrace them.

Suggested Action Items

  1. Look for an opportunity to share your resources with others. For example, borrow a book from your local library rather than buying a new one, create an opportunity to share gardening tools with a neighbor, or organize a community swap for books, toys, clothing, or other products. You will then become part of the circular economy.
  2. Learn about the environmental challenges faced in your local community. Identify one place where you’d like to focus your attention on the health of the land. Do your part to help preserve it through charity, clean-up or solar projects, or sponsoring a wildlife habitat.
  3. Create community opportunities to learn faith-based wisdom on sustainability and creation care, like through a book club, learning circle, or after-school program. See www.interfaithsustain.com for further resources.

Torah portion of Vayera

Resilience of Trees

Genesis 18:4 – Let a little water be brought; bathe your feet and recline under the tree. Rabbeinu Chananel asked why the angels revealed themselves to Abraham under a tree.35

He answered that in doing so they revealed a message to Abraham: “You, like a tree, will flourish even in your old age,” as it says in the book of Job, “For a tree has hope; if it is cut it will again renew itself, and its trunk will never cease,”36 and in the words of the Psalmist, “He shall be as a tree planted beside streams of water, which brings forth its fruit in its season. Its leaves do not wilt; and whatever it does prospers.”37

Abraham’s resilience and prosperity are compared to a tree. Indeed, trees are one of the most resilient organisms, specifically against drought. This is increasingly important in light of climate change causing unpredictable rainfall, extreme weather events, and stronger pests that threaten forests.38 Contemporary researchers have discovered that diverse “forests with trees that employ a high diversity of traits related to water use suffer less of an impact from drought.”39

They are also more resilient to forest fires.

Veal Then and Now

Genesis 18:7 – Then Abraham ran to the herd, took a calf, tender and choice, and gave it to a servant-boy, who hastened to prepare it.

Radak explains that the calf was “fatty.”40 A Biblical fatty calf would have been naturally well fed by its mother and not overworked, so that it could put on weight. Today, however, calves are raised unnaturally for veal, kept in cramped conditions, and fed artificial fluids.

Regarding the permissibility of this modern way of raising calves, Rabbi Moshe Feinstein, one of the greatest twentieth-century authorities on Jewish law, writes, “Regarding the new method of fattening calves in special, narrow stalls where they don’t even have enough room to take a few steps, and they are not fed any normal animal feed nor are they allowed to suckle at all but instead are fed with fatty liquids from which they derive no pleasure at all and they are also frequently ill because of this and require all kinds of medication: Those who perform this (the fattening) are surely guilty of the prohibition of causing pain to animals. For even though it (pain) is permitted when there is a purpose, for example to slaughter them for food or to use them for plowing or transport, etc. but not for senseless pain, which is forbidden even if someone makes monetary gain from it… In any case, it is forbidden to cause pain to an animal, to feed it food which it doesn’t enjoy, which causes pain, or which causes it to be ill.”41

Morality and Ecology – by Rabbi Yuval Cherlow42

Genesis 19:24 – The Lord rained upon Sodom and Gomorrah sulfurous fire from the Lord out of heaven.

Two cosmic catastrophes unfold in the book of Genesis. In the flood, God brings waters down from the Heavens to destroy almost all life. In the second, the utter devastation of Sodom and Gomorrah, an area previously known as a fertile and lush “Garden of God,”43 becomes a desolate land “that cannot be sown, nor sprout, and no grass shall rise up upon it, like the upheaval of Sodom and Gomorrah… which God overturned in His anger, and His wrath.”44

One of the connections we see between these two events is the word that the Torah employs in both cases—to destroy. When God relates to Noah that He will bring the flood, He says, “I am about to destroy [mashkheetam] them from the earth.”45 In the case of Sodom we see the same word applied: “When God destroyed (beshakhet) the cities of the plain…”46The Torah does not elaborate on the sin of Sodom, but the underpinnings are expressed later in the prophecy of Ezekiel: Sodom “…had pride, excess bread, and peaceful serenity, but did not strengthen the hand of the poor and the needy.”47 The prophet’s description, combined with what the Torah reveals to us, gives us the following picture: The people of Sodom insisted on preserving their high quality of living to such an extent that they established a principle not to let the poor and homeless reside in their city.

Consequently, when a destitute person would come seeking help, he or she would revoke their right to any welfare, public or private! In this rule, the Sodomites figured they would preserve an elite upper class community that could monopolize the profits that the bountiful land offered, without having to distribute any revenues to a “lower class” of people. An opinion in the Mishnah further strengthens this picture of moral depravity when it defines the Sodomite as one who says, “What’s mine is mine and what’s yours is yours.”48 The Mishnah decries a man who wishes to remove himself from the social responsibility of
welfare by closing himself and his wealth from others, even if he makes the claim that he is not taking away from anyone else.

But the Torah also uses the verb “to destroy” in relation to the environment, regarding the prohibition of wanton destruction during a military siege: “Do not destroy [tashkhit] the trees.”49

What could be the connection between the corruption of the generation of the flood, the people of Sodom, and environmental sins? Humanity itself is part and parcel of its environment and is not separate from it. Having been created in the image of God, we may think that we are detached from creation.

The central point in the connection between moral behavior and environmental behavior comes from the understanding that both behaviors go hand in hand. One without the other corrupts the Divine vision for human action. That is, a society may be passionate about preserving its natural environment while maintaining a complete disregard for the welfare of its citizens. Sodom is a perfect example of this, where they cared so much for their “garden of God” that they refused to aid anyone in need.

In effect, the people of Sodom’s perverted ways were extremely unsustainable—causing God to turn one of the most fertile and lush ecosystems on earth into what today is infamous for its barrenness and desolation. From the mistakes of the people of Sodom, we can learn the essential character traits that allow one to live in balance with the Creator and creation.

The moral human being is devoted to the holiness and purity of life, refrains from harming others, and sacrifices some personal pleasure for an ethical and upright path. When we are capable of fulfilling this ideal, we will naturally be triumphant in attaining the great spiritual task of infusing our religious/moral lifestyle with one that is also environmentally sustainable.

Suggested Action Items

1. Look for an opportunity to be generous to another human being this week. For example: give money to the poor, schedule a time to volunteer at a local shelter, or find time to join a local team which is fulfilling a community need.
2. Learn about the challenges of environmental justice and environmental racism. These topics will show you how our environmental choices can disproportionately impact others.
3. Focus your attention on living “in balance” with the Creator and creation. One way to do this is by focusing on buying and preparing only as much food as you will eat. Clean out your refrigerator and note which food items have gone to waste so that you will buy less next time.

1 Midrash Genesis Rabbah 39:1.
2 Yosef Y. Jacobson, “The Burning Palace,” Chabad, September 11, 2002,
www.chabad.org/library/article_cdo/aid/59473/jewish/The-Burning-Palace.htm.
3 Jonathan Sacks, Radical Then, Radical Now (London: Continuum, 2000), 49-53.
4 Alexandria Symonds, “Amazon Rainforest Fires: Here’s What’s Really Happening,” The New York Times, August
28, 2019, https://www.nytimes.com/2019/08/23/world/americas/amazon-fire-brazil-bolsonaro.html.
5 This content was produced by Canfei Nesharim, a branch of Grow Torah. It is available at
http://canfeinesharim.org/lech-lecha-joining-together-for-justice-in-the-land/.
6 Ha’amek Davar on 13:6 and Rabbi Samson Raphael Hirsch on Genesis 13:6 in The Pentateuch, Efraim Oratz ed.,
Gertrude Hirschler trans. (NY: Judaica Press, 1986). This idea has a precedent in Pesikta Rabati 83.
7 Ibn Ezra also translates yachdav as yachid—united, and not yachad—together.
8 Adamah, Alexandra Kuperman, Farmer D, et al.
9 Hazon, Hava VeAdam, Torat Hateva, et al.
10 Commentary to Genesis 26:1.
11 Midrash Genesis Rabbah 64:2. Famine occurs in the time of Isaac in Genesis 26:12 and in the time of Jacob in
Genesis 41:56.
12 See Seder Olam for the dates that Abraham went to Egypt and the date that Jacob left for Egypt.
13 Stephen Devereux, “Famine in the Twentieth Century,” IDS Working Papers 105, January 2000.
14 IPCC, “Climate Change and Land, An IPCC: Special Report on Climate Change, Desertification, Land
Degradation, Sustainable Land Management, Food Security, and Greenhouse Gas Fluxes in Terrestrial
Ecosystems,” Summary for Policymakers, IPCC, 2019, https://www.ipcc.ch/site/assets/uploads/2019/08/4.-
SPM_Approved_Microsite_FINAL.pdf.
15 Seth Borenstein and Jamey Keaten, “UN Climate Report: Change Land Use to Avoid a Hungry Future,” Phys.org,
August 8, 2019, https://phys.org/news/2019-08-climate-hungry-future.html.
16 Ralbag on Genesis 14:3.
17 Rashi on Genesis 13:10.
18 Guy Pe’er and Uriel N. Safriel, Climate Change Israel National Report: Impact, Vulnerability and Adaptation (Israel: Blaustein Institute for Desert Research, Ben-Gurion University of the Negev, October 2000).
19 Israel Water Authority, “Saving the Dead Sea,” http://www.water.gov.il/Hebrew/Water-Environment/Dead-Sea/DocLib1/saving-dead-sea-eng.pdf (accessed June 18, 2020).
20 This is distinct from clay, which is referred to as chomer. Onkelos translates chemar into Aramaic as chemra, which is understood by language scholars to refer to bitumen or asphalt. See Marcus Jastrow, Dictionary of the Targumim, 1926
https://www.sefaria.org.il/Jastrow%2C_%D7%97%D6%B5%D7%99%D7%9E%D6%B8%D7%A8%D6%B8%D7%90?lang=he. See also Safar Ivrit. “Chimer and Chomer”. https://www.safa-ivrit.or/form/khomer.php (accessed January 3, 2020).
21 “Bitumen,” Energy Education, University of Calgary, last modified June 25, 2018,
https://energyeducation.ca/encyclopedia/Bitumen.
22 Rabbi Aryeh Kaplan writes, “Even now asphalt is found in the Dead Sea region. The Romans referred to it as Mer Aspheltitus, the Asphalt Sea, as it was known to cast up lumps of asphalt. Rabbi Aryeh Kaplan. Living Torah Commentary to Genesis 14:10, 65. Josephus Wars 4:8:4; Tacitus, Histoires 5:6.
23 Asaf Oron et al., “Early Maritime Activity on the Dead Sea: Bitumen Harvesting and the Possible Use of Reed Watercraft,” Journal of Maritime Archaeology 10, no. 1, April 2015, 65-88, https://doi.org/10.1007/s11457-015-9135-2.
24 Genesis 14:11.
25 “What Are the Oil Sands?”, Canadian Association of Petroleum Producers, https://www.capp.ca/oil/what-are-the-oil-sands/ (accessed March 1, 2020).
26 Stephen Leahy, “This is the World’s Most Destructive Oil Operation—and It’s Growing,” National Geographic, April 11, 2019, https://www.nationalgeographic.com/environment/2019/04/alberta-canadas-tar-sands-is-growing-but-indigenous-people-fight-back/.
27 Lisa Song, “Why Tar Sands Oil Is More Polluting and Why It Matters,” Reuters, May 22, 2012,
https://www.reuters.com/article/idUS201043482520120522.
28 Genesis Rabbah 42:7 quoted by Rashi on Genesis 14:10.
29 Jacobson et al., “100% Clean and Renewable Wind, Water, and Sunlight All-Sector Energy Roadmaps for 139 Countries of the World,” Joule 1, 108-121 September 6, 2017, Elsevier Inc. http://dx.doi.org/10.1016/j.joule.2017.07.005.
30 Maharal, Netivot Olam, Netiv HaOsher 1:4.
31 See Rashi on Genesis 13:7.
32 Abraham Ibn Ezra, “God Everywhere” (1089-1164).
33 Jeremy Benstein, The Way into Judaism and the Environment (Vermont: Jewish Lights Publishing, 2006), 142,
citing Elie Wiesel.
34 Rabbi Mordechai Hochman, “Footnote 1 based on the Midrash,” in “The Bird That Brings Life to the Carcasses,” Yeshiva Beit El, published Kislev 5, 5770, https://www.yeshiva.org.il/midrash/12714.
35 Rabbeinu Chananel on Genesis 18:4.
36 Job 14:7-9.
37 Psalms 1:3.
38 Moises Velasquez-Manoff, “Can Humans Help Trees Outrun Climate Change?” The New York Times, April 25,
2019, https://www.nytimes.com/2019/04/25/climate/trees-climate-change.html?searchResultPosition=7.
39 William R. L. Anderegg et al., “Hydraulic Diversity of Forests Regulates Ecosystem Resilience During Drought,” Nature 561, no. 7724, September 2018, https://doi.org/10.1038/s41586-018-0539-7.
40 Radak on Genesis 18:7.
41 Responsa Igrot Moshe, Even Haezer, vol iv 92. Quoted in “The environment in Jewish Thought and Law,” Saul Stokar, Sviva Israel (2018), 28.
42 This content was produced by Canfei Nesharim, a branch of Grow Torah. It is available at
http://canfeinesharim.org/wp-content/uploads/2014/05/Parsha-vayera-sin-of-sedom-Rabbi-Cherlow-sourcesheet.pdf.
43 Genesis 13:10.
44 Deuteronomy 29:22.
45 Genesis 6:13.
46 Ibid, 19:29.
47 Ezekiel 16:49.
48 Mishnah Avot 5:10.
49 Deuteronomy 20:19.