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 4169

Narrated Yazid bin Abi Ubaid:

I said to Salama bin Al-Akwa`, "For what did you give the Pledge of allegiance to Allah's Messenger (ﷺ) on the day of Al-Hudaibiya?" He replied, "For death (in the Cause of Islam.).

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا حَاتِمٌ، عَنْ يَزِيدَ بْنِ أَبِي عُبَيْدٍ، قَالَ قُلْتُ لِسَلَمَةَ بْنِ الأَكْوَعِ عَلَى أَىِّ شَىْءٍ بَايَعْتُمْ رَسُولَ اللَّهِ صلى الله عليه وسلم يَوْمَ الْحُدَيْبِيَةِ‏.‏ قَالَ عَلَى الْمَوْتِ‏.‏
Reference : Sahih al-Bukhari 4169
In-book reference : Book 64, Hadith 211
USC-MSA web (English) reference : Vol. 5, Book 59, Hadith 487
  (deprecated numbering scheme)