John Calvin Commentary Deuteronomy 22:30

"A man shall not take his father`s wife, and shall not uncover his father`s skirt." — Deuteronomy 22:30 (ASV)

A man shall not take his father’s wife. Since Moses does not refer here to any other kinds of incest, but speaks only of that with a stepmother, it is probable that what he had more fully set forth previously, he here briefly recalled to the minds of the Israelites under a single heading. At any rate, the prohibition of one offense does not open the gate to other abominations. The expression he adds, nor discover his father’s skirt, means that the father is exposed to shame when the stepson has no regard for decency and goes in to his stepmother. Perhaps he alludes to the sin of Ham, who betrayed his ungodliness by exposing the shame of his father (Genesis 9:22).