Sahih (Sahih al-Bukhari)
حَدَّثَنَا أَبُو عَاصِمٍ، عَنْ يَزِيدَ بْنِ أَبِي عُبَيْدٍ، عَنْ سَلَمَةَ، قَالَ بَايَعْنَا النَّبِيَّ صلى الله عليه وسلم تَحْتَ الشَّجَرَةِ فَقَالَ لِي " يَا سَلَمَةُ أَلاَ تُبَايِعُ ". قُلْتُ يَا رَسُولَ اللَّهِ قَدْ بَايَعْتُ فِي الأَوَّلِ. قَالَ " وَفِي الثَّانِي ".
Narrated Salama:We gave the oath of allegiance to the Prophet (ﷺ) under the tree. He said to me, "O Salama! Will you not give the oath of allegiance?" I replied, "O Allah's Messenger (ﷺ)! I have already given the oath of allegiance for the first time." He said, (Give it again) for the second time