The Prophet wrote the (marriage contract) with 'Aisha while she was six years old and consummated his marriage with her while she was nine years old and she remained with him for nine years (i.e. till his death).
حَدَّثَنَا قَبِيصَةُ بْنُ عُقْبَةَ، حَدَّثَنَا سُفْيَانُ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ عُرْوَةَ، تَزَوَّجَ النَّبِيُّ صلى الله عليه وسلم عَائِشَةَ وَهْىَ ابْنَةُ سِتٍّ وَبَنَى بِهَا وَهْىَ ابْنَةُ تِسْعٍ وَمَكَثَتْ عِنْدَهُ تِسْعًا.
• Sahih al-Bukhari, 5158
• Sahih al-Bukhari, Vol. 7, Book of Marriage, Hadith 88
• Sahih al-Bukhari, Book of Marriage, Hadith 88