Asma', daughter of Yazid ibn as-Sakan al-Ansariyyah, was divorced in the time of the Messenger of Allah ﷺ. 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.  

أَنَّهَا طُلِّقَتْ عَلَى عَهْدِ رَسُولِ اللَّهِ ﷺ وَلَمْ يَكُنْ لِلْمُطَلَّقَةِ عِدَّةٌ فَأَنْزَلَ اللَّهُ ﷻ حِينَ طُلِّقَتْ أَسْمَاءُ بِالْعِدَّةِ لِلطَّلاَقِ فَكَانَتْ أَوَّلَ مَنْ أُنْزِلَتْ فِيهَا الْعِدَّةُ لِلْمُطَلَّقَاتِ