Leviticus 18:14
Thou shalt not uncover the nakedness of thy father's brother, thou shalt not approach to his wife: she is thine aunt.
Thou shalt not uncover the nakedness of thy father's brother,.... Which Gersom understands of committing sodomy with him, on which account he was doubly guilty, partly because of lying with a male, and partly because of uncovering the nakedness of his father's brother; but it rather seems at first sight as if the sense was, that a woman should not marry her father's brother, that is, her uncle, as a man might not marry his aunt, whether by father or mother's side, as in
Leviticus 18:12; but Jarchi directs to a better sense than either, when he asks, what is his nakedness? in answer to which he recites the following clause as explanative of it:
thou shall not approach to his wife; in the use of the bed, as the Targum of Jonathan adds, that is, to lie with her, her husband being living, or to marry her, he being dead:
she is thine aunt: even as a father's or mother's sister, only they are aunts by blood, this by marriage or affinity: in the Targums of Onkelos and Jonathan it is, she is the wife of thy father's brother; and as Aben Ezra, she is accounted as thine aunt, and so marriage with her prohibited; and the same holds good of a father's brother's wife, which being not mentioned, the same writer says, we have need of the tradition which expresses that and also of a father's sister's husband; for if marriage with a father's brother's wife is unlawful, then marriage with a father's sister's husband must be so too; for a father's sister's husband stands in the same degree or line of affinity as a father's brother's wife; and it is a sure rule, that in whatsoever degree or line of affinity males are forbid to marry females, in the same females are forbid to marry males.