It is narrated from Asma' bint Yazid bin al-Sakan al-Ansariyyah (may Allah be pleased with her) that she (that is, Asma' bint Yazid, may Allah be pleased with her) was divorced in the time of the Messenger of Allah (peace and blessings be upon him), and at that time there was no waiting period ('iddah) for divorced women. So Allah, exalted be His praise, revealed the verses concerning the waiting period of divorce when Asma' was divorced. She was the first woman concerning whom the waiting period of divorce was revealed.
[Hasan. Recorded by al-Sijistani 2281]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العدد / 15378