Albert Barnes Commentary Deuteronomy 23:7-8

"Thou shalt not abhor an Edomite; for he is thy brother: thou shalt not abhor an Egyptian, because thou wast a sojourner in his land. The children of the third generation that are born unto them shall enter into the assembly of Jehovah." — Deuteronomy 23:7-8 (ASV)

The Edomite, as descended from Esau the twin brother of Jacob , and the Egyptian, as from that nation which had for long shown hospitality to Joseph and his brothers, were not to be objects of abhorrence. The oppression of the Egyptians was perhaps regarded as the act of the Pharaohs rather than the will of the people (Exodus 11:2–3); and at any rate was not to cancel the memory of preceding hospitality (Deuteronomy 23:8).

In their third generation – that is, the great-grandchildren of the Edomite or Egyptian alien: compare the similar phrase in Exodus 20:5.