(11) 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.

Verse 11. - Incest with a half-sister on the father's side is again forbidden. Perhaps "the prohibition refers to the son by a first marriage, whereas verse 9 treats of the son by a second marriage" (Keil).

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.The nakedness of thy father's wife's daughter,.... Either the daughter of his father by another wife, which seems to be countenanced by what follows:

begotten of thy father, she is thy sister; but then this coincides with what is prohibited, Leviticus 18:9, "the daughter of thy father"; that is, by another woman than a man's mother, only with this difference, that there is added, or "daughter of thy mother", that is, by another man than a man's own father; so that there is a prohibition of a sister whether by father or mother's side; here only as by the father's side, and so is only a part of that law; and, as some think, is for the confirmation of it, as Aben Ezra observes; or else the sense, as he thinks, is, that if a man marries a woman, and she has a little daughter by a former husband, that daughter may not be given in marriage to his son; and so the Septuagint version finishes this clause first, before it gives the other, which it considers as distinct from it, thus, "the shame of thy father's, wife's daughter thou shalt not uncover"; and then makes a distinct law of the latter; "she that is begotten of thy father is thy sister, thou shalt not uncover her shame"; but then this last falls in with Leviticus 18:9, the Sadducees, as Aben Ezra also observes, by whom he means the Karaites, interpret it not of a mother's daughter, but of one brought up and educated by a man's father, and so is his adopted daughter, whom his son might not marry; and thus with the Romans it is said (g), that adoptive kindred hindered marriage between parents and children altogether; and among brethren so far forth as the loss of freedom did not intervene: some understand this law in this light, as De Dieu, that in Leviticus 18:9; the son of a second marriage is forbidden to marry with an half sister of the first marriage, whether she is the father's daughter, that is, which the father had by his deceased wife, or the mother's daughter, that is, which his mother had by a deceased husband; but here the son of a first marriage is forbidden with a half sister of a second marriage, which his mother-in-law has bore to his father, and is therefore called "the daughter of thy father's wife"; that is, of thy stepmother, but so the same may be said to be "begotten of thy father"; and therefore one begotten in a former marriage may not be understood; but then as this forbids the marriage of a brother with a sister, that is, of the same father, though not of the same mother, it falls in within the former law; wherefore some (h) have been of opinion, that this law forbids a man to marry the daughter of a woman whom his father has taken to wife, who was his deceased brother's wife, upon the law in Deuteronomy 25:5; by which marriage she became the father's daughter, and the son's sister; wherefore they take the phrase, "begotten of thy father", to signify "being akin" to thy father; which, if it can be established, makes a distinct law: Jarchi observes, on this phrase, "the daughter of thy father's wife","this teaches that a man is not guilty concerning his sister that is by an handmaid or stranger; therefore it is said, the daughter of thy father's wife, namely, one that was fit for marriage."

thou shalt not uncover her nakedness; See Gill on Leviticus 18:9.

(g) Paulus in Mosaic. & Roman. Leg. Collat. Titus 6. a Pithaeo. (h) Bertram. Lucubrat. Franktal. c. 6. Pool in loc.