Sahih Bukhari · Hadith 4222
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi) - كتاب المغازى
حدثنا إسحاق، حدثنا يحيى بن صالح، قال حدثنا معاوية هو ابن سلام عن يحيى، عن أبي قلابة، أن ثابت بن الضحاك، أخبره أنه، بايع النبي صلى الله عليه وسلم تحت الشجرة.
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.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).