It is narrated from Hazrat Mughirah (may Allah be pleased with him) that there are two matters about which I will not ask anyone, because I have seen the Noble Prophet (peace and blessings be upon him) doing those actions. One is the imam performing prayer behind someone from his own congregation; I saw the Noble Prophet (peace and blessings be upon him) once performing one rak‘ah of Fajr prayer behind Hazrat Abdur Rahman bin Awf (may Allah be pleased with him). The second is wiping over leather socks (khuffs), because I have seen the Noble Prophet (peace and blessings be upon him) wiping over leather socks.