Divorce
Ṣaḥīḥ al-Bukhārī 5251
مُرْهُ فَلْيُرَاجِعْهَا، ثُمَّ لِيُمْسِكْهَا حَتَّى تَطْهُرَ ثُمَّ تَحِيضَ، ثُمَّ تَطْهُرَ، ثُمَّ إِنْ شَاءَ أَمْسَكَ بَعْدُ وَإِنْ شَاءَ طَلَّقَ قَبْلَ أَنْ يَمَسَّ، فَتِلْكَ الْعِدَّةُ الَّتِي أَمَرَ اللَّهُ أَنْ تُطَلَّقَ لَهَا النِّسَاءُ
murhu falyurājiʿhā, thumma liyumsikhā ḥattā taṭhura thumma taḥīḍa, thumma taṭhura, thumma in shāʾa amsaka baʿdu wa-in shāʾa ṭallaqa qabla an yamassa, fatilka al-ʿiddah at-tī amara-Llāh an tuṭallaqa lahā an-nisāʾu
Transliteration generated from the Arabic vowel marks
The full narration
Narrated `Abdullah bin `Umar:that he had divorced his wife while she was menstruating during the lifetime of Allah's Messenger (ﷺ) . `Umar bin Al-Khattab asked Allah's Messenger (ﷺ) about that. Allah's Messenger (ﷺ) said, "Order him (your son) to take her back and keep her till she is clean and then to wait till she gets her next period and becomes clean again, whereupon, if he wishes to keep her, he can do so, and if he wishes to divorce her he can divorce her before having sexual intercourse with her; and that is the prescribed period which Allah has fixed for the women meant to be divorced
Source
Ṣaḥīḥ al-Bukhārī · 5251