Sahih Bukhari Volume 4, Book 56, Hadith Number 777.

Narated By Al-Bara : We were one-thousand-and-four-hundred persons on the day of Al-Hudaibiya (Treaty), and (at) Al-Hudaibiya (there) was a well. We drew out its water not leaving even a single drop. The Prophet sat at the edge of the well and asked for some water with which he rinsed his mouth and then he threw it out into the well. We stayed for a short while and then drew water from the well and quenched our thirst, and even our riding animals drank water to their satisfaction.