Sahih Bukhari
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
Volume: 005 / Book Number: 059 / Hadith Number: 482
Narrated Said bin Al-Musaiyab:
That his father was amongst those who had given the Pledge of allegiance (to the Prophet ) beneath the Tree, and the next year when they went towards the Tree, they were not able to recognize it.