Amr ibn Muhajir reported on the authority of his father: Asma’, daughter of Yazid ibn as-Sakan al-Ansariyyah, was divorced in the time of the Messenger of Allah (peace be upon him). No waiting period was prescribed for a divorced woman (at that time). When Asma’ was divorced, Allah, the Exalted, sent down the injunction of waiting period for divorce. She is the first of the divorced women about whom the verse relating to waiting period was sent down.
Sunan Abi Dawud, Book 13, Hadith 107