Surah Al-Mujadilah, ayah 3

58:3

وَٱلَّذِينَ يُظَٰهِرُونَ مِن نِّسَآئِهِمۡ ثُمَّ يَعُودُونَ لِمَا قَالُواْ فَتَحۡرِيرُ رَقَبَةٖ مِّن قَبۡلِ أَن يَتَمَآسَّاۚ ذَٰلِكُمۡ تُوعَظُونَ بِهِۦۚ وَٱللَّهُ بِمَا تَعۡمَلُونَ خَبِيرٞ ٣

Walladhīna yuzāhirūna min nisā'ihim thumma ya'ūdūna limā qālū fatahrīru raqabatim min qabli an yatamāssā dhālikum tū'azūna bihī wallāhu bimā ta'malūna khabīr

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.