John Gill Commentary 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." — Leviticus 18:11 (ASV)

The nakedness of your father's wife's daughter
Either the daughter of his father by another wife, which seems to be countenanced by what follows: begotten of your father, she is your sister; but then this coincides with what is prohibited, (Leviticus 18:9), "the daughter of your father"; that is, by another woman than a man's mother, only with this difference, that there is added, or "daughter of your 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 your father's, wife's daughter you shall not uncover"; and then makes a distinct law of the latter; "she that is begotten of your father is your sister, you shall not uncover her shame"; but then this last falls in with (Leviticus 18:9).

The Sadducees, as Aben Ezra also observes, 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 ^F7, that adoptive kindred hindered marriage between parents and children altogether; and among brethren insofar 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 your father's wife"; that is, of your stepmother, but so the same may be said to be "begotten of your 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 ^F8 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, based on 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 your father", to signify "being related" to your father; which, if it can be established, this makes a distinct law.

Jarchi observes, on this phrase, "the daughter of your father's wife," "this teaches that a man is not guilty concerning his sister who is by an handmaid or stranger; therefore it is said, the daughter of your father's wife, namely, one who was fit for marriage."

you shall not uncover her nakedness; (See Gill on Leviticus 18:9).

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FOOTNOTES:

• F7: Paulus in Mosaic. & Roman. Leg. Collat. tit. 6. a Pithaeo.
• F8: Bertram. Lucubrat. Franktal. c. 6. Pool in loc.