Leviticus 18:11

The nakedness of thy father's wife's daughter, begotten of thy father, she is thy sister, thou shalt not uncover her nakedness.

The nakedness of thy father's wife's daughter, begotten of thy father. Since it seems not very probable that an enactment so nearly resembling that mentioned, Leviticus 18:9, would, in so brief a table of marriage laws, be repeated, the presumption is, that this refers to the daughter of a family reared up by a deceased father's brother, who, according to the levirate law (Deuteronomy 25:5), espoused the widow, whose children by him were reckoned her former husband's; and so close a kindred was established between the two branches that a marriage between a son of the one and a daughter of the other was prohibited as an incestuous connection. The persons "near of kin" with whom it is declared (Leviticus 18:6) unlawful to marry are specified (Leviticus 18:7) to be:

(1) Those in the first (Leviticus 18:7) and second (Leviticus 18:10), or collaterals in the first (Leviticus 18:9; Leviticus 18:11; Leviticus 18:17) and second (Leviticus 18:12), degrees of consanguinity;

(2) Those in the first (Leviticus 18:8; Leviticus 18:15; Leviticus 18:17) and second (Leviticus 18:17), or collaterals in the first (Leviticus 18:16) and second (Leviticus 18:14), degrees of affinity.

Though there may be some possible connections not specifically described, it can be easily inferred from those that are instanced, whether they are lawful or forbidden; as, for instance, when it is said (Leviticus 18:7), man may not marry his mother, a daughter on similar ground cannot be married to her father; or (Leviticus 18:13) a man may not marry his aunt, it follows, by parity of reason, that a woman may not marry her uncle (Selden, 'De Uxore. Heb.;' Dwight's 'Hebrew Wife').

In the primeval age of the world there was a necessity for brothers and sisters to marry; and in patriarchal times, when the marriage law was not authoritatively defined, great latitude was allowed in forming the tie between husband and wife (see the notes at Genesis 20:12; Genesis 29:21; and at Exodus 6:20). But on the establishment of the Mosaic economy, not only was this liberty restricted, but a boundary line strictly drawn, which no one, without incurring severe penalties, could overpass. This code became the marriage law in Israel; and there can be no doubt that in raising a fence around the honour and rights of the female sex it tended to elevate the tone of domestic and social morality among that people.