Musnad Ahmad 937:156

'Abd al-'Aziz ibn 'Abd al-Samad al-'Ammi narrated to us, Abu 'Imran al-Jawni narrated to us, from 'Abdullah ibn al-Samit, from Abu Dharr, who said: I was behind the Prophet, peace and blessings of Allah be upon him, when we went out from the outskirts of Medina. He said: "O Abu Dharr, perform the prayer at its time. If you come and the Imam has already prayed, you have already secured your prayer before that. And if you come and he has not prayed, you pray with him, and your prayer will be a supererogatory act for you, and you will have secured your prayer." "O Abu Dharr, what do you think if the people become so hungry that you cannot reach your mosque due to exhaustion, or you cannot return to your bed due to exhaustion, then what will you do?" I said: Allah and His Messenger know best. He said: "Practice restraint." He said: "O Abu Dharr, what do you think if the people die until a house is worth a slave, then what will you do?" I said: Allah and His Messenger know best. He said: "Be patient." He said: "O Abu Dharr, what do you think if the people are killed until the stones of al-Zayt are submerged in blood, how will you act?" I said: Allah and His Messenger know best. He said: "Enter your house." I said: O Messenger of Allah, what if someone enters upon me? He said: "Join those whom you are from." I said: Should I carry my weapon? He said: "Then you would be participating." I said: What should I do, O Messenger of Allah? He said: "If you fear that the radiance of the sword will dazzle you, then cast a part of your garment over your face; he will return with your sin and his sin."