Charles Ellicott Commentary Leviticus 18:10

"The nakedness of thy son`s daughter, or of thy daughter`s daughter, even their nakedness thou shalt not uncover: for theirs is thine own nakedness." — Leviticus 18:10 (ASV)

The nakedness of thy son’s daughter. From this prohibition it is inferred that a man must not marry his own daughter. If a granddaughter, who is a degree further removed from him, is proscribed, how much more his own daughter. Hence the canonical law during the Second Temple deduced from this passage that “whoever has relations with a woman, even by way of fornication, and begets a daughter, she is forbidden to him.” Still, when the mother is expressly forbidden to the son , it is strange that the daughter should have been passed over in silence, and be left to inference.

It is therefore more than probable that a word has dropped out of the text, and that originally it stood here, “the nakedness of thy daughter and of thy son’s daughter,” etc. That this is not a solitary instance where the text has suffered from disarrangement we will soon have occasion to see in Leviticus 18:11.