Musnad Abu Ya'la al-Mawsili 128:24

Abu Khaythama narrated to us, Abd al-Rahman narrated to us, from Sufyan, from Amr ibn Amir, who said: I heard Anas saying: The Messenger of Allah (may Allah bless him and grant him peace) used to perform ablution for every prayer. He said: I said, "And you, how do you do?" He said: "We used to pray the prayer with one ablution, as long as we did not break it."