وَالَّذينَ يُظاهِرونَ مِن نِسائِهِم ثُمَّ يَعودونَ لِما قالوا فَتَحريرُ رَقَبَةٍ مِن قَبلِ أَن يَتَماسّا ۚ ذٰلِكُم توعَظونَ بِهِ ۚ وَاللَّهُ بِما تَعمَلونَ خَبيرٌ

And those who pronounce thihar 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 Allah is Acquainted with what you do.