Matthew Poole and continuators on Deuteronomy 22:30

30 A man shall not take his fathers wife , nor discover his fathers skirt .

To Wife. So this respects the state, and the next branch speaks of the act onely.

His Mother in law. See Levit. 18. 8. and 20. 11. 1 Cor. 5. 1.

(i. e.) The skirt of the Mothers Garment, i. e. the nakedness, which is here called his fathers skirt, because his Father and Mother were one flesh, or because his Father alone had the right to uncover it. The phrase is taken from the ancient custome or ceremonie of the Bridegrooms spreading the skirt of his Garment over the bride, to signifie his right to her, and authority over her, and his obligation to the marriage duty. See Ruth. 3. 9. Ezek. 16. 8.

Marginal references: Lev. 18. 8.