Hadith 10:863
Abu Bakr narrated to us, he said: Ya'la ibn 'Ubayd narrated to us, from 'Abd al-Malik, from 'Ata', regarding the man who swore an oath (ila') against his wife until four months had passed: How does she observe the waiting period ('iddah)? He said: She observes a waiting period of three menstrual cycles (quru').
حدثنا أبو بكر قال نا يعلى بن [ عبيد ] عن عبد الملك عن عطاء في الرجل آلى من امرأته حتى مضت أربعة أشهر كيف تعتد قال تعتد ثلاثة قروء