We read in the next section how the church is preserved. The family of Abraham represents the church of Jesus Christ throughout all ages, and here is God's manifestation to him.
How many do the opposite, and stint what they do not expect to receive back in return. Some start and do not follow through, but Abraham is determined to do better than his word and shows himself to be a man who says nothing lightly.
This 18th chapter is often criticised by cynical people, and it is claimed that it has elements in it that are copied from heathen mythology. If you ever come across that kind of remark and comment, it is pure speculation; it is nonsense. Most certainly there are elements of what appears in Genesis 18 to be found in heathen mythology, but they are most probably copied from here. This is the refined and, in a literary sense, self-consistent original, and the events of the Book of Genesis and the historical record of these chapters were known far and wide. It is not surprising that some elements of them, in distorted and corrupted and partial form, should crop up in other literature in those days. This is God's revelation, and is perfectly constructed, and it is consistent with the running themes of the entire early chapters of the book of Genesis.