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 Allah's Apostle took the Ar-Ridwan Pledge of allegiance. Then I went to Sa'id bin Musaiyab and informed him about it. Said said, "My father said that he was amongst those who had given the Pledge of allegiance to Allah's Apostle 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 Said said (perhaps ironically) "The companions of the Prophet could not recognize it; nevertheless, you do recognize it; therefore you have a better knowledge."