Imam Sadiq (a.s) said: “Imam Ali's servant named Ghanbar really liked him and would always follow him at night with his sword in order to protect him. One night Imam Ali (a.s) noticed him and asked him what he was doing. He said: “I am following you.” The Imam (a.s) asked: “Are you trying to protect me from heavenly or earthly creatures?” He replied: “I am guarding you against earthly creatures.” The Imam (a.s) said: “Please go home since no one on Earth can do me any harm unless God' permits so.” Then Ghanbar returned home.