Volume 5 · Book 59 · Hadith 489
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 AlHudaibiya) beneath the Tree.
— Sahih Bukhari, Volume 5, Book 59: Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi), Hadith #489