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. (Using translation from Abū Dāʾūd 2281)   

أَنَّهَا طُلِّقَتْ عَلَى عَهْدِ رَسُولِ اللهِ ﷺ وَلَمْ يَكُنْ لِلْمُطَلَّقَةِ عِدَّةٌ فَأَنْزَلَ اللهُ جَلَّ ثَنَاؤُهُ حِينَ طُلِّقَتْ أَسْمَاءُ بِالْعِدَّةِ لِلطَّلَاقِ فَكَانَتْ أَوَّلَ مَنْ أُنْزِلَ فِيهَا الْعِدَّةُ لِلطَّلَاقِ  

[Machine] When the verse of women in Surah Al-Baqarah was revealed, regarding divorce and the death of a husband, Ubayy ibn Ka'b said, “O Messenger of Allah, some people from the people of Madinah say that there are still women about whom nothing has been mentioned." The Prophet asked, "What are they?" Ubayy replied, "Those who are young and old, those who are pregnant." Then the verse was revealed, "{And those who no longer expect menstruation among your women - if you doubt, then their period is three months, and [also for] those who have not menstruated. And for those who are pregnant, their term is until they give birth.}" [Al-Talaq 4]  

لَمَّا نَزَلَتْ عِدَّةُ النِّسَاءِ فِي سُورَةِ الْبَقَرَةِ فِي الْمُطَلَّقَةِ وَالْمُتَوَفَّى عَنْهَا زَوْجُهَا قَالَ قَالَ أُبَيُّ بْنُ كَعْبٍ يَا رَسُولَ اللهِ إِنَّ أُنَاسًا مِنْ أَهْلِ الْمَدِينَةِ يَقُولُونَ قَدْ بَقِيَ مِنَ النِّسَاءِ مَا لَمْ يُذْكَرْ فِيهِ شَيْءٌ قَالَ وَمَا هُوَ؟ قَالَ الصِّغَارُ وَالْكِبَارُ ذَوَاتُ الْحَمْلِ قَالَ فَنَزَلَتْ {وَاللَّائِي يَئِسْنَ مِنَ الْمَحِيضِ مِنْ نِسَائِكُمْ إِنِ ارْتَبْتُمْ فَعِدَّتُهُنَّ ثَلَاثَةُ أَشْهُرٍ وَاللَّائِي لَمْ يَحِضْنَ وَأُولَاتُ الْأَحْمَالِ أَجَلُهُنَّ أَنْ يَضَعْنَ حَمْلَهُنَّ} [الطلاق 4]