Sahih al-Bukhari, Book 64, Hadith 211 (In-Book) ⓘ
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 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.
also referenced under: Hadith 4169 (DarusSalam) & Volume 5, Book 59, Hadith 487 (USC-MSA)