It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the wife of Thabit bin Qays (may Allah be pleased with him) obtained a khul', so the Prophet (peace and blessings be upon him) ordered her to observe a waiting period ('iddah) of one menstrual cycle.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11464