Musannaf Ibn Abi Shayba 27:87

Abu Usama narrated to us, from Zakariya, from Abu Ishaq, from Al-Bara’ who said: We arrived on the day of Al-Hudaybiyah and found that the first of the people had drunk its water. The Prophet, peace and blessings of Allah be upon him, sat by the well, then he called for a bucket from it. He took what remained in it, then he spat into it and supplicated to Allah, so its water increased until the people quenched their thirst from it.