Abul Juhaim b. al-Harith b. as-Simma said that once when coming from the direction of Bi’r Jamal* the Prophet was met by a man who saluted him, but the Prophet did not respond to his salutation till he went towards the wall and wiped his face and his hands. Then he responded to his salutation.
*A well in Medina.
(Bukhari and Muslim.)