Those who divorce their wives by Zihar, then wish to retract the words they uttered, shall have to free a slave before they touch each other. This is enjoined as a penalty for doing so. Allah is well-aware of all your actions.
Meaning:-
Zihar is a term denoting a custom of the Arabs in the days of ignorance. In case of disagreement with their wives they used to say to them, “You are for me like the back of my mother.” After saying this, they used to take their wives as their real mother in being prohibited for them, and the ties of marriage were held to have been broken for good.