Chapter 1: The Book of Purification
It was narrated from 'Amr bin 'Amir that Anas mentioned: "The Messenger of Allah (ﷺ) was brought a small vessel (of water) and he performed Wudu'." I said: "Did the Messenger of Allah (ﷺ) perform Wudu' for every prayer?" He said: "Yes." He said: "What about you?" He said: "We used to pray all the prayers so long as we did not commit Hadath." He said: "And we used to pray all the prayers with (one) Wudu'."
Sunan an-Nasa'i 131