Chapter 1: The Book of Purification
It was narrated that Hudhaifah said: "I was walking with the Messenger of Allah (ﷺ) and he came to some people' s garbage dump and urinated while standing up. I turned to go away, but he called me back (to conceal him), and I was just behind him. Then when he had finished, he performed Wudu' and wiped over his Khuffs."
Sunan an-Nasa'i 18