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."
Arabic/English book reference: Vol. 1, Book 1, Hadith 18