When I set out for Hajj, I passed by some people offering a prayer, I asked, "What is this mosque?" They said, "This is the Tree where Messenger of Allah ﷺ took the Ar-Ridwan Pledge of allegiance. Then I went to Saʿid bin Musaiyab and informed him about it. Saʿid said, "My father said that he was amongst those who had given the Pledge of allegiance to Messenger of Allah ﷺ beneath the Tree. He (i.e. my father) said, "When we set out the following year, we forgot the Tree and were unable to recognize it. "Then Saʿid said (perhaps ironically) "The companions of the Prophet ﷺ could not recognize it; nevertheless, you do recognize it; therefore you have a better knowledge."  

انْطَلَقْتُ حَاجًّا فَمَرَرْتُ بِقَوْمٍ يُصَلُّونَ قُلْتُ مَا هَذَا الْمَسْجِدُ قَالُوا هَذِهِ الشَّجَرَةُ حَيْثُ بَايَعَ رَسُولُ اللَّهِ ﷺ بَيْعَةَ الرُّضْوَانِ فَأَتَيْتُ سَعِيدَ بْنَ الْمُسَيَّبِ فَأَخْبَرْتُهُ فَقَالَ سَعِيدٌ حَدَّثَنِي أَبِي أَنَّهُ كَانَ فِيمَنْ بَايَعَ رَسُولَ اللَّهِ ﷺ تَحْتَ الشَّجَرَةِ قَالَ فَلَمَّا خَرَجْنَا مِنَ الْعَامِ الْمُقْبِلِ نَسِينَاهَا فَلَمْ نَقْدِرْ عَلَيْهَا فَقَالَ سَعِيدٌ إِنَّ أَصْحَابَ مُحَمَّدٍ ﷺ لَمْ يَعْلَمُوهَا وَعَلِمْتُمُوهَا أَنْتُمْ فَأَنْتُمْ أَعْلَمُ