Tirmidhi

´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."

'Abdullah bin Abbas (may Allah be pleased with them both) says that the wife of Thabit bin Qais obtained khul‘ (divorce at the wife’s instance) from her husband during the time of the Prophet (peace and blessings of Allah be upon him), so the Prophet (peace and blessings of Allah be upon him) ordered her to observe the waiting period of one menstrual cycle. © Imam Tirmidhi says:
1- This hadith is hasan ghareeb,
2- «مختلعہ» (a woman who obtains khul‘) — there is a difference of opinion among the scholars regarding her waiting period. Most of the scholars among the Companions and others say that the waiting period of «مختلعہ» is the same as that of a divorced woman, i.e., three menstrual cycles. This is also the view of Sufyan Thawri and the scholars of Kufa, and Ahmad and Ishaq bin Rahwayh also hold this view,
3- And some of the scholars among the Companions and others say that the waiting period of «مختلعہ» is one menstrual cycle,
4- Ishaq bin Rahwayh says that if someone adopts this view, it is a strong view.