Musannaf Ibn Abi Shayba 20:24

Abu Bakr narrated to us, he said: Muhammad ibn Sawa narrated to us, from Sa’id ibn Abi ‘Aruba, from Abu al-Tufayl Sa’id ibn Hamal, from ‘Ikrimah, he said: The waiting period (‘iddah) of the woman who seeks khul’ (divorce initiated by the wife) is one menstrual cycle, as decreed by the Messenger of Allah, peace and blessings of Allah be upon him, regarding Jamilah bint Salul.