Matthew Poole and continuators on Leviticus 18:7

7 The nakedness of thy father or the nakedness of thy mother, shalt thou not uncover: she is thy mother , thou shalt not uncover her nakedness.

Heb and, put for that is, or to wit, as it is oft used. Here it notes, that the nakedness of the father, and the nakedness of the mother are one and the same thing, because they two are one flesh, and therefore her nakedness is his also. Which further appears because the mother onely is mentioned in the following words, which contain the reason of the law.

And therefore even nature teacheth thee to abhor such incest. Yet the Persians used to marry their mother, therein worse than the very Camels, whom no force will drive to that act with their dams.