Surah Al-Mujadila, Verse 3

وَٱلَّذِينَ يُظَٰهِرُونَ مِن نِّسَآئِهِمۡ ثُمَّ يَعُودُونَ لِمَا قَالُواْ فَتَحۡرِيرُ رَقَبَةٖ مِّن قَبۡلِ أَن يَتَمَآسَّاۚ ذَٰلِكُمۡ تُوعَظُونَ بِهِۦۚ وَٱللَّهُ بِمَا تَعۡمَلُونَ خَبِيرٞ٣

wa-alladhīna yuẓāhirūna min nisāihim thumma yaʿūdūna limā qālū fataḥrīru raqabatin min qabli an yatamāssā dhālikum tūʿaẓūna bihi wal-lahu bimā taʿmalūna khabīrun

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.