(14) Thy father’s brother, thou shalt not approach to his wife.—That is, according to the ancient legal interpretation, a nephew is to have no commerce with her during her husband’s lifetime, nor marry her when his uncle is dead. Those who transgressed this law had not only to bear their sin, but were doomed to die without issue. (See Leviticus 20:20.)

Leviticus 18:14. Thy father’s brother — Thou shalt not marry thy uncle’s wife, as is explained in the next words.

18:1-30 Unlawful marriages and fleshly lusts. - Here is a law against all conformity to the corrupt usages of the heathen. Also laws against incest, against brutal lusts, and barbarous idolatries; and the enforcement of these laws from the ruin of the Canaanites. God here gives moral precepts. Close and constant adherence to God's ordinances is the most effectual preservative from gross sin. The grace of God only will secure us; that grace is to be expected only in the use of the means of grace. Nor does He ever leave any to their hearts' lusts, till they have left him and his services.Thy father's sister - The instance of Amram and Jochebed Exodus 6:20 seems to show that marriage with an aunt was not considered wrong by the Israelites when they were in Egypt. 6. None of you shall approach to any that is near of kin to him—Very great laxity prevailed amongst the Egyptians in their sentiments and practice about the conjugal relation, as they not only openly sanctioned marriages between brothers and sisters, but even between parents and children. Such incestuous alliances Moses wisely prohibited, and his laws form the basis upon which the marriage regulations of this and other Christian nations are chiefly founded. This verse contains a general summary of all the particular prohibitions; and the forbidden intercourse is pointed out by the phrase, "to approach to." In the specified prohibitions that follow, all of which are included in this general summary, the prohibited familiarity is indicated by the phrases, to "uncover the nakedness" [Le 18:12-17], to "take" [Le 18:17, 18], and to "lie with" [Le 18:22, 23]. The phrase in this sixth verse, therefore, has the same identical meaning with each of the other three, and the marriages in reference to which it is used are those of consanguinity or too close affinity, amounting to incestuous connections. Of thy father’s brother, i.e. of his wife, as the next words explain it. And as a man may not marry his aunt, so neither may a woman marry her uncle, there being altogether the same distance in kindred, and the selfsame reason of the law. And for the examples of Abraham, Amram, Othniel, &c., to the contrary, they were before the publication of this law, by which it pleased God to restrain the liberty allowed formerly, when the holy seed was in a narrower compass, and fewer persons, which altered the case. For in that regard there was a time when God allowed brethren and sisters to marry, to wit, when there were no other in the world, which was the case of Adam’s immediate children. We learn from hence that the same degrees are forbidden in consanguinity or kindred by blood, and in affinity or kindred by marriage.

She is thine aunt: some infer from hence that it is unlawful for cousin-germans, or the children of brethren and sisters, to marry. But there is not the same reason, nor the same degree of distance, for my uncle or aunt are nearer akin to me than their children are. Yet because it seems doubtful to many, and may hereafter prove occasion of grievous perplexities of mind, especially to tender and scrupulous consciences, Christian prudence directs us to choose the safest way, there being so great a latitude of unquestionable persons.

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.

Thou shalt not uncover the nakedness of thy {g} father's brother, thou shalt not approach to his wife: she is thine aunt.

(g) Which your uncle discovers.