Thou shalt not uncover the nakedness of thy father's sister,.... His aunt by his father's side, an instance of which we have in Amram, Ex 6:20; and Maimonides says , an aunt was forbidden whether she was a father's sister in lawful wedlock or in fornication:she [is] thy father's near kinswoman; or, the rest of thy father ; the residue of his flesh, one of the same flesh and blood with him; wherefore, as he could not marry her himself, so his son likewise was too near akin to enter into such a relation with her.
Hilchot Issure Biah, c. 2. sect. 5.