Sunan an-Nasa'i, Book 39, Hadith 11 (In-Book) ⓘ
It was narrated that Yazid bin Abi 'Ubaid said: "I said to Salamah bin Al-Akwa': 'What pledge did you make to the Prophet on the Day of Al-Hudaibiyyah?' He said: 'For death."'
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا حَاتِمُ بْنُ إِسْمَاعِيلَ، عَنْ يَزِيدَ بْنِ أَبِي عُبَيْدٍ، قَالَ قُلْتُ لِسَلَمَةَ بْنِ الأَكْوَعِ عَلَى أَىِّ شَىْءٍ بَايَعْتُمُ النَّبِيَّ صلى الله عليه وسلم يَوْمَ الْحُدَيْبِيَةِ قَالَ عَلَى الْمَوْتِ .
also referenced under: Hadith 4159 (Reference) & Volume 5, Book 39, Hadith 4164 (DarusSalam)