Al-Mujadila · 58:2

2. Those who do Ẓihār to their wives, by saying to them: “You are for me like the back of my mother”, have lied in this statement of theirs. Their wives are not their mothers; their mothers are only those women who gave birth to them, and when they make such statements they are uttering a disgusting, false statement. But indeed, Allah is overlooking and forgiving: He has legislated an atonement for you to free you of the sin.