Language:
كتاب المغازى
64  
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
(35)
Chapter: The Ghazwa of Al-Hudaibiya
(35)
باب غَزْوَةِ الْحُدَيْبِيَةِ
Sahih al-Bukhari 4171

Narrated Abu Qilaba:

that Thabit bin Ad-Dahhak had informed him that he was one of those who had given the Pledge of allegiance (of Al-Hudaibiya) beneath the Tree.

حَدَّثَنَا إِسْحَاقُ، حَدَّثَنَا يَحْيَى بْنُ صَالِحٍ، قَالَ حَدَّثَنَا مُعَاوِيَةُ ـ هُوَ ابْنُ سَلاَّمٍ ـ عَنْ يَحْيَى، عَنْ أَبِي قِلاَبَةَ، أَنَّ ثَابِتَ بْنَ الضَّحَّاكِ، أَخْبَرَهُ أَنَّهُ، بَايَعَ النَّبِيَّ صلى الله عليه وسلم تَحْتَ الشَّجَرَةِ‏.‏
Reference : Sahih al-Bukhari 4171
In-book reference : Book 64, Hadith 213
USC-MSA web (English) reference : Vol. 5, Book 59, Hadith 489
  (deprecated numbering scheme)