Fath al-Rabbani

Saeed bin Musayyib narrates from his father, and his father was among those who pledged allegiance (Bay'at al-Ridwan) to the Holy Prophet (peace and blessings be upon him) under the tree. He said: When we went the following year with the intention of Hajj, it became difficult for us to recognize the place of that tree. (That is, it became difficult to determine under which tree and at which place we had pledged allegiance.) If that place has become clear to you, then you would know better about it. The purpose of the companion of the Messenger of Allah (peace and blessings be upon him) in saying this is that even in the following year, we could not have certain knowledge of that tree and its place. If someone after us has come to know about it, then his knowledge would be more than ours. The meaning is that no one has certain knowledge of it. (Abdullah Rafiq)