I met Bara bin Azib and said to him, "Blessed are you! You accompanied the Prophet ﷺ and pledged allegiance to him under the tree."He replied, "My nephew, you do not know what we introduced after him."
لقيت البراء بن عازب رضي الله عنه فقلت: طوبى لك، صحبت النبي ﷺ وبايعته تحت الشجرة، فقال: يا ابن أخي، إنك لا تدري ما أحدثنا بعده.
Bukhari narrated it in "Al-Maghazi" (4170) from Ahmad bin Ishkab, who said, Muhammad bin Fudayl narrated to us, from Ala bin Musayab, from his father, who said, and he mentioned it.