At the same time God spoke to Abraham, and promised that his seed was to be multiplied as the sand of the sea; and that his predicted seed would live in a land not his own, while his posterity would endure slavery in a hostile country for four hundred years, but would afterwards be restored to liberty. Then his name was changed, as well as that of his wife, by the addition of one letter; so that instead of Abram he was called Abraham, and, instead of Sara, she was called Sarra.
The mystery involved in this is by no means trifling, but it is not the part of this work to treat of it. At the same time, the law of circumcision was enjoined on Abraham, and he had by a maid-servant a son called Ishmael. Moreover, when he himself was a hundred years old, and his wife ninety, God promised that they should have a son Isaac, the Lord having come to him along with two angels. Then the angels being sent to Sodom, found Lot sitting in the gate of the city. He supposed them to be human beings, and welcomed them to share in his hospitality, and provided an entertainment for them in his house, but the wicked youth of the town demanded the new arrivals for impure purposes.
Lot offered them his daughters in place of his guests, but they did not accept the offer, having a desire rather for things forbidden, and then Lot himself was laid hold of with vile designs. The angels, however, speedily rescued him from danger, by causing blindness to fall upon the eyes of these unchaste sinners. Then Lot, being informed by his guests that the town was to be destroyed, went away from it with his wife and daughters; but they were commanded not to look back upon it.
His wife, however, not obeying this precept (in accordance with that evil tendency of human nature which renders it difficult to abstain from things forbidden), turned back her eyes, and is said to have been at once changed into a monument. As for Sodom, it was burned to ashes by fire from heaven. And the daughters of Lot, imagining that the whole human race had perished, sought a union with their father while he was intoxicated, and hence sprung the race of Moab and Ammon.
Source: Sacred History (New Advent)