א”ר אחא כתיב כי מלאה הארץ חמס מפניהם (ברא’ ו:יג). ומה היה חמסן? הוה בר נש נפיק טעין קופה מלאה תורמוסין והיו מתכוונין ונוטלין פחות משוה פרוטה דבר שאינו יוצא בדיינין. אמר רבי חייה בר ווה רבה נאמר כאן רבה (פס’ ה) ונאמר להלן זעקת סדום רבה ( בר’ יח:כ) כמעשי אילו כך מעשי אילו. בבא מציעא ד:ב טו,א

The Mishnah (Bava Metsi’ah 4:2) teaches that if one pays for fruit but does not actually have the chance to take it from the seller, the seller has the ability to change his mind and return the money.  Nevertheless, the Rabbis maintained that there is an impropriety in going back on one’s word and that for doing so a person will incur Divine Retribution similar to the People of the Generation of the Flood.

נתן לו מעות ולא משך לו פירות יכול לחזור בו אבל אמרו מי שפרע מאנשי דור המבול עתיד להפרע ממי שאינו עומד בדבורו

What does the case of the Mishnah, going back on one’s word have to do with the Flood? An insight may be found in the Talmud Yerushalmi.

Rabbi Aha explains that the sin of the People of the Generation of the Flood was that they systematically stole less than the value of a perutah, an amount which can not be claimed in court. When a person would leave his house with merchandise, the people around him would swipe small amounts from him. Although the amounts taken by each individual were too small to be brought to justice, the people would end up practically robbing him of all of his possessions.

The connection would appear to be that one who goes back on his word and one who steals less than the value of a perutah both commit a crime for which their is no legal recourse. When the courts can not bring a people to justice, God does.

Rabbi Hiyya bar Abba likens the sins of the People of the Generation of the Flood with that of the People of Sodom. “Before they had a chance to lie down the people of Sodom surrounded the house from the young to the elderly, all of the people who were at a distance” (Gen. 19:5). The Scripture paints a picture of a thoroughly corrupt Sodom. The young, like the elderly, the far like the close banded together against Lot’s guests in their common endeavor of acting out their immoral desires.

The People of the Flood, like the People of Sodom were corrupt through and through. The manner in which the people of the Flood banded together against their culprit  presumes a state of corruption like that which existed in the Generation of the People of Sodom.

Rabbi Hiyya bar Abba focuses on the state of lawlessness in the two generations. It would seem that in his opinion the idea in the case of our Mishnah is God’s extreme sensitivity to anything that smacks of lawlessness.