Al-Mujadila 58:3

Wallatheena yuthahiroonamin nisa-ihim thumma yaAAoodoona lima qaloofatahreeru raqabatin min qabli an yatamassa thalikumtooAAathoona bihi wallahu bimataAAmaloona khabeer

And those who pronounce ẓihār from their wives and then [wish to] go back on what they said - then [there must be] the freeing of a slave before they touch one another. That is what you are admonished thereby; and Allāh is Aware of what you do.

Those who declare Zihār against their wives, then retract what they said, obligated on them is to free the neck (of a slave) before the two (spouses) touch one another. This is what you are advised, and Allah is well aware of what you do.