Thy father’s wife’s daughter. — If this clause stood alone it would denote the daughter of a man’s stepmother by another or previous husband, since “father’s wife” in Hebrew always denotes stepmother (see Leviticus 18:8; Leviticus 20:11; Deuteronomy 23:1, Deut. 26:20), in which case the man and the maiden, though no blood relations at all, would be forbidden to each other by virtue of the damsel’s mother having married the man’s father. It would thus differ from Leviticus 18:9, where the maiden is a half-sister either by the same father or the same mother.
Begotten of thy father. — Literally, the birth, or offspring of thy father (see Leviticus 18:9), that is, though the daughter of the stepmother, she is begotten by the same father, and hence is his half-sister on the father’s side, which is exactly the same case already prohibited in the first clause of Leviticus 18:9. Hence to avoid a senseless repetition of the same prohibition we must either regard this clause as having crept into the text from a marginal gloss, or we must correct the first letter of the disjunctive particle in Leviticus 18:9, which would make it “the nakedness of thy sister, the daughter of thy father and the daughter of thy mother.” Accordingly, Leviticus 18:9 prohibits marriage with a full sister, whilst the verse before us forbids it with a half-sister. The latter is the more probable, since intermarriage between entire stepbrother and stepsister has always been, and still is, legitimate among the Jews.