Sahih Muslim Book 4, Hadith Number 1018.

Chapter : The excellence of the prayer and the way it is begun and the excellence of Ruku’ and moderation in it and prostration and moderation in it, etc.

Shu’ba narrated the same on the basis of two authorities and in the Hadith transmitted by Hakam (the words are): The people began to get water that was left out of his (the Prophet’s) ablution.