Leviticus 18:14

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.