The Messenger of Allah (ﷺ) came from the privy. A man met him near Bir Jamal and saluted him. The Messenger of Allah (ﷺ) did not return the salutation until he came to a wall and placed his hands on the wall and wiped his face and hands; he then returned the man's salutation.
Sunan Abi Dawud Book 1, Hadith 331