Leviticus 18:14

“Thou shalt not uncover the nakedness of thy father’s brother, etc.] 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 (<031812>Leviticus 18:12,13); 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…”

“18:14 Having sexual relations with your aunt would dishonor your uncle. In turn, this would also dishonor your father (see 20:20).”

“Lev 20:20 Leviticus 18:15”

“So, again, with the wife of the father's brother, because the nakedness of the uncle was thereby uncovered. The threat held out in Lev 20:19 and Lev 20:20 against the alliances prohibited in Lev 18:12-14, is that the persons concerned should bear their iniquity or sin, i.e., should suffer punishment in consequence (see at Lev 5:1); and in the last case it is stated that they should die childless. From this it is obvious that sexual connection with the sister of either father or mother was not to be punished with death by the magistrate, but would be punished with disease by God Himself. Leviticus 18:15”