Gen 18, 19

Visit of the Three Angels.
(& Destruction of the Cities of the Plain) (J)

This splendidly told, beautiful story is marred for us by certain passages. Its motives are various – to account for the extraordinary physical characteristics of the Dead Sea region, and to give some plausible account of the origin of the kindred peoples Moab and Ammon, are obvious. But it also deals with the problem of the suffering of the innocent with and for the guilty, which is generally thought not to have arisen as early as the J source. Whether the destruction of the cities was a historical event, the memory of which was handed down in tradition for 1000 years or more, or the product of poetical imagination, must be a matter of opinion.

1-15
"Entertaining angels (or the gods) unawares" is a frequent motive in the stories of antiquity. The three men prove to be Yahweh and two angels. Abraham's hospitality is a fine example of that virtue as practised in the East.
The word translated butter signifies curdled milk.

when the season, etc. Apparently = a year hence. In v.14 (the angel of) Yahweh speaks of Yahweh as of a third person.

Gen 21. 1-7.

The birth of Isaac (J, E, and P). Here Abraham's age is emphasised, not Sarah's.