Leviticus 20:21

“And if a man shall take his brother’s wife, etc.] To his wife, whether in his life, as the Targum of Jonathan adds, or whether after his death, unless when there is no issue, then he was obliged to it by another law, (<052505>Deuteronomy 25:5); which is now ceased, and the law in (<031816>Leviticus 18:16); here referred to, stands clear of all exceptions: it [is] an unclean thing; or a “separation” f728 from which a man should remove and keep at a distance, as from menstruous women, of whom this word is used; and so denotes that it is by all means to be avoided, as an abominable and detestable thing; and it is observed that of all copulations it is only used of this: and the Jewish writers,…”

“His brother's wife - Except in the case allowed by God, Deu 25:5. Leviticus 20:27”

“his brother's: Lev 18:16; Mat 14:3, Mat 14:4 an unclean thing: Heb. a separation Leviticus 20:22”