Sahih Muslim Book 20, Hadith Number 4579.

Chapter : It is good on the part of a leader to take the oath of allegiance from his forces when intending to fight, and an account of the allegiance of God’s pleasure under the tree.

It has been narrated (through a different chain of transmitters) on the authority of Abu Zubair who heard Jabir being questioned as to whether the Holy Prophet (may peace be upon him) took the oath of fealty at Dhu’l-Hulaifa. He said: No! But he offered his prayers at that place, and he administered the oath of fealty nowhere except near the tree in (the plain of Hudaibiya). Ibn Juraij said that he was informed by Abu Zabair who heard Jabir b. Abdullah say: The Holy Prophet (may peace be upon him) prayed over the well at Hudaibiya (as a result of which its scanty water rose up and increased so as to be sufficient for the 1400 or 1500 men who had encamped at the place).