´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."
Hadith ReferenceSunan at-Tirmidhi / The Book on Divorce and Li'an / Hadith: 1185