Sahih al-Bukhari 4165
Sahih al-Bukhari · Book 64: Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi) · The Ghazwa of Al-Hudaibiya
Narrated Tariq:
حَدَّثَنَا قَبِيصَةُ ، حَدَّثَنَا سُفْيَانُ ، عَنْ طَارِقٍ ، قَالَ ذُكِرَتْ عِنْدَ سَعِيدِ بْنِ الْمُسَيَّبِ الشَّجَرَةُ فَضَحِكَ فَقَالَ أَخْبَرَنِي أَبِي وَكَانَ، شَهِدَهَا .
(The tree where the Ridwan Pledge of allegiance was taken by the Prophet) was mentioned before Sa`id bin Al-Musaiyab. On that he smiled and said, "My father informed me (about it) and he had witnessed it (i.e. the Pledge) ."