Hadith 10:1172
Abu Bakr narrated to us, he said: Hafs bin Ghiyath narrated to us, from al-A’mash, from Ibrahim, from Umar and Abdullah, that they both said: Whoever divorces his wife, he has more right to take her back as long as she has not performed ghusl from her third menstruation.
حدثنا أبو بكر قال نا حفص بن غياث عن الأعمش عن إبراهيم عن عمر وعبد الله انهما قالا من طلق امرأته فهو أحق برجعتها ما لم تغتسل من حيضتها الثالثة