לֹא־יִקַּ֥ח אִ֖ישׁ אֶת־אֵ֣שֶׁת אָבִ֑יו וְלֹ֥א יְגַלֶּ֖ה כְּנַ֥ף אָבִֽיו׃ (ס)
Sifrei Devarim
(Devarim 23:1) "A man shall not take the wife of his father": From here they ruled: A man may marry the ravished of one's father and the enticed of his father. R. Yehudah forbids the ravished of his father and the enticed of his father, it being written "A man shall not take the wife of his father."