AR-Rubayyi bint Mu'awwidh bin Al-Afra narrated:that she got a Khul during the time of the Prophet. So the Prophet ordered her - or: she was ordered - that she observe an Iddah of a menstruation

Ibn Abbas narrated that :The wife of Thabit bin Qais was granted a Khul from her husband during the time of the Prophet. So the Prophet ordered her to observe an Iddah of a menstruation