17 If a man takes his sister, a daughter of his father or a daughter of his mother, and sees her nakedness, and she sees his nakedness, it is a disgrace, and they shall be cut off in the sight of their people; he has uncovered his sister's nakedness, he shall be subject to punishment. 18 If a man lies with a woman having her sickness and uncovers her nakedness, he has laid bare her flow and she has laid bare her flow of blood; both of them shall be cut off from their people. 19 You shall not uncover the nakedness of your mother's sister or of your father's sister, for that is to lay bare one's own flesh; they shall be subject to punishment. 20 If a man lies with his uncle's wife, he has uncovered his uncle's nakedness; they shall be subject to punishment; they shall die childless. 21 If a man takes his brother's wife, it is impurity; he has uncovered his brother's nakedness; they shall be childless.
Matthew Henry's Commentary on Leviticus 20:17-21
Commentary on Leviticus 20:10-27
(Read Leviticus 20:10-27)
These verses repeat what had been said before, but it was needful there should be line upon line. What praises we owe to God that he has taught the evil of sin, and the sure way of deliverance from it! May we have grace to adorn the doctrine of God our Saviour in all things; may we have no fellowship with unfruitful works of darkness, but reprove them.