Hadith 10:16
Abu Bakr narrated to us, he said: Sufyan ibn ‘Uyaynah narrated to us, from Hisham ibn Hujayr, from Tawus, who said: The divorce of the Sunnah is that a man divorces his wife while she is in a state of purity (tuhr) without having had intercourse with her, then he leaves her until her waiting period (‘iddah) expires.
حدثنا أبو بكر قال نا سفيان بن عيينة عن هشام بن [ حجير ] عن طاوس قال طلاق السنة أن يطلق الرجل امرأته طاهرا في غير جماع ثم يدعها حتى تنقضي عدتها