Leviticus 18:11

11. Father’s wife’s daughter Knobel finds this distinction between this and Leviticus 18:9, namely, that the words “father’s wife” include the mother as well as the stepmother, and thus specifically state the full sister. Others find no prohibition of the marriage of a full sister, as there is none of the marriage of a daughter, simply because such unions, like parricide, were regarded as crimes so unnatural that they never could occur. But the Assyrians, and especially the Egyptians, against whose customs Israel was warned in Leviticus 18:3, married full sisters. This fact sustains Knobel.