صحيح البخاري
5  
Sahih al-Bukhari
Salamah ibn al-Akwaʿ (may Allah be pleased with him) reported:
"We gave the pledge of allegiance to the Prophet ﷺ under the tree. He said to me: 'O Salamah, will you not give the pledge?' I said: 'O Messenger of Allah, I have already pledged the first time.' He said: '[Give it] a second time as well.'" Reference: Sahih al-Bukhari 7208
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».
Grade: Ṣaḥīḥ
Arabic/English book reference : Book 5, Hadith 21