Language:
كتاب النكاح
67  
Wedlock, Marriage (Nikaah)
(39)
Chapter: Giving one's young children in marriage
(38)
باب إِنْكَاحِ الرَّجُلِ وَلَدَهُ الصِّغَارَ
Sahih al-Bukhari 5133

Narrated `Aisha:

that the Prophet (ﷺ) married her when she was six years old and he consummated his marriage when she was nine years old, and then she remained with him for nine years (i.e., till his death).

حَدَّثَنَا مُحَمَّدُ بْنُ يُوسُفَ، حَدَّثَنَا سُفْيَانُ، عَنْ هِشَامٍ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ ـ رضى الله عنها ـ أَنَّ النَّبِيَّ صلى الله عليه وسلم تَزَوَّجَهَا وَهْىَ بِنْتُ سِتِّ سِنِينَ، وَأُدْخِلَتْ عَلَيْهِ وَهْىَ بِنْتُ تِسْعٍ، وَمَكَثَتْ عِنْدَهُ تِسْعًا‏.‏
Reference : Sahih al-Bukhari 5133
In-book reference : Book 67, Hadith 69
USC-MSA web (English) reference : Vol. 7, Book 62, Hadith 64
  (deprecated numbering scheme)