Leviticus 20:17

"And if a man shall take his sister, his father's daughter, or his mother's daughter, and see her nakedness, and she see his nakedness; it is a shameful thing; and they shall be cut off in the sight of the children of their people: he hath uncovered his sister's nakedness; he shall bear his iniquity. And if a man shall lie with a woman having her sickness, and shall uncover her nakedness; he hath made naked her fountain, and she hath uncovered the fountain of her blood: and both of them shall be cut off from among their people. And thou shalt not uncover the nakedness of thy mother's sister, nor of thy father's sister; for he hath made naked his near kin: they shall bear their iniquity. And if a man shall lie with his uncle's wife, he hath uncovered his uncle's nakedness: they shall bear their sin; they shall die childless. And if a man shall take his brother's wife, it is impurity: he hath uncovered his brother's nakedness; they shall be childless."

Regarding the penalties of childlessness, or dying childless, although technically different (for example, one who had children, by surviving all of them, could die childless), probably refer to the same penalty, and what was likely meant is that any children born to such unions would be credited to the deceased brother or uncle in the genealogical rolls of the people, rather than to the natural father, after the manner of children born in Levirate marriages. "It cannot be supposed that a perpetual miracle was maintained through all the ages of history"[9] merely to prevent the birth of any children to such marital unions.

Clements' opinion that Leviticus 20:21 "precludes Levirate marriages"[10] is inaccurate, because, we noted above, the very penalties assigned to such violations presuppose or anticipate Levirate marriages (Deuteronomy 25:5-10).

It is not absolutely clear that any of the sins mentioned in this paragraph incurred the death penalty, but, in any event, they were considered to be very serious violations of sacred law. The impression is justified that there was, for some reason, a lesser degree of guilt imputed in the crimes mentioned here.