Sunan an-Nasai 17999
In-book no 3263أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا عَبْثَرٌ، عَنْ مُطَرِّفٍ، عَنْ أَبِي إِسْحَاقَ، عَنْ أَبِي عُبَيْدَةَ، قَالَ قَالَتْ عَائِشَةُ تَزَوَّجَنِي رَسُولُ اللَّهِ صلى الله عليه وسلم لِتِسْعِ سِنِينَ وَصَحِبْتُهُ تِسْعًا .
It was narrated that Abu 'Ubaidah said: "Aishah said: 'The Messenger of Allah married me when I was nine and I lived with him for nine years.'"