Sunan Ibn Majah, Book 10, Hadith 2099 (In-Book) ⓘ

It was narrated that 'Abdullah said: "Divorce according to the Sunnah means divorcing her with one divorce in each cycle when she is pure, then when she becomes pure the third time, then he pronounces divorce again, and after that she must wait one more menstrual cycle."

حَدَّثَنَا عَلِيُّ بْنُ مَيْمُونٍ الرَّقِّيُّ، حَدَّثَنَا حَفْصُ بْنُ غِيَاثٍ، عَنِ الأَعْمَشِ، عَنْ أَبِي إِسْحَاقَ، عَنْ أَبِي الأَحْوَصِ، عَنْ عَبْدِ اللَّهِ، قَالَ طَلاَقُ السُّنَّةِ يُطَلِّقُهَا عِنْدَ كُلِّ طُهْرٍ تَطْلِيقَةً فَإِذَا طَهُرَتِ الثَّالِثَةَ طَلَّقَهَا وَعَلَيْهَا بَعْدَ ذَلِكَ حَيْضَةٌ ‏.‏