They shall be cut off in the sight of their people— Some, again, believe that this punishment implies that they shall be separated from the communion and covenant of Israel; and not, that they should be put to death. They think, that the punishments assigned in the other verses seem to prove this.
Related Commentaries of Leviticus 20:17
Leviticus 20:17
17 And if a man shall take his sister, his father's daughter, or his mother's daughter, and see her nakedness, and she see his nakedness; it is a wicked thing; and they shall be cut off in the sight of their people: he hath uncovered his sister's nakedness; he shall bear his iniquity.