I set out for Hajj and passed by some people praying. I asked, "What is this mosque?"They replied, "This is the tree where the Messenger of Allah ﷺ received the Pledge of Ridwan."So I went to Saeed bin Musayab and told him about it. Saeed said, "My father told me that he was among those who pledged allegiance to the Messenger of Allah ﷺ under the tree. He said, 'When we set out the following year, we forgot its location and could not find it.'"Then Saeed remarked, "The Companions of Muhammad ﷺ did not know it, yet you people claim to know it. So you must know better than they did."
انطلقت حاجا فمررت بقوم يصلون قلت: ما هذا المسجد قالوا: هذه الشجرة، حيث بايع رسول الله ﷺ بيعة الرضوان. فأتيت سعيد بن المسيب فأخبرته فقال سعيد: حدثني أبي أنه كان فيمن بايع رسول الله ﷺ تحت الشجرة، قال: فلما خرجنا من العام المقبل نسيناها، فلم نقدر عليها. فقال سعيد: إن أصحاب محمد ﷺ لم يعلموها وعلمتموها أنتم، فأنتم أعلم.
Bukhari narrated it in the Book of Maghazi (4163), and Muslim narrated it in the Book of Imarah (77:1859), both through the route of Tariq bin Abdul-Rahman, who said, and then he related it. Muslim also narrated it in the Book of Jihad (77:1859) through other routes from Tariq bin Abdul-Rahman, except that he did not mention the masjid or the prayer in it.