מדרש על בראשית 19:8

Another explanation: "He who walketh with wise men shall be wise" (ibid.). This refers to Lot, who walked with our father Abraham, and learned of his good deeds and ways. They said: What did our father Abraham do? He made for himself a house opposite to Haran, and he received everyone who entered into or went out from Haran, and he gave him to eat and to drink. He said to them: Say ye, The God of Abraham is the only one in the universe. || When Lot came to Sodom he did likewise. When they made proclamation in Sodom: All who strengthen the hand of the poor or needy with a loaf of bread shall be burnt by fire, he was afraid of the men of the city, (and did not venture) to do so by day, but he did it by night, as it is said, "And the two angels came to Sodom at even; and Lot sat in the gate of Sodom" (Gen. 19:1). Why did Lot sit in the gate of Sodom? Because he was afraid of the men of the city, (and did not venture) to act (charitably) by day, but he did so by night. He saw the two angels walking in the street of the city, and he thought that they were wayfarers in the land, and he ran to meet them. He said to them: Come and lodge ye overnight in my house, eat and drink, and ye shall go your way in peace. But the men would not accept this for themselves, and he took them by the hand against their will, and brought them inside his house, as it is said, "And he urged them greatly" (Gen. 19:8).

A certain young man of the people of that city saw them, and he ran and told all the men of that city, and they all gathered together at the door of the house to do according to their wont, even deeds of sodomy, as it is said, "And they called unto Lot, and said unto him, || Where are the men who came to thee to-night? bring them forth unto us that we may know them" (Gen. 19:5). What did Lot do? Just as Moses gave his life for the people, so Lot gave up his two daughters instead of the two angels, as it is said, "Behold, now, I have two daughters" (Gen. 19:8). But the men would not agree (and did not accept them). What did the angels do to them? They smote them with blindness until the dawn of the (next) morning. All were treated with (measure for) measure. Just as he had taken them by the hand without their will and taken them into his house, so they took hold of his hand, and the hand of his wife, and the hand of his two daughters, and took them outside the city, as it is said, "But he lingered; and the men laid hold upon his hand" (Gen. 19:16). And they said to them: Do not look behind you, for verily the Shekhinah of the Holy One, blessed be He, has descended in order to rain upon Sodom and upon Gomorrah brimstone and fire. The pity of 'Edith the wife of Lot was stirred for her daughters, who were married in Sodom, and she looked back behind her to see if they were coming after her or not. And she saw behind the Shekhinah, and she became a pillar of salt, as it is said, "And his wife looked back from behind him, and she became a pillar of salt" (Gen. 19:26).