Musnad Ahmad

It is narrated from Sayyiduna Sa’d bin Abi Waqqas (may Allah be pleased with him) that on the day of the Battle of the Trench, I saw a man who was protecting himself with a shield; sometimes he would raise the shield above his nose, sometimes lower it. Seeing this, I turned my attention to my quiver, took out a blood-stained arrow from it, and fitted it to the bow. When he lowered the shield, I aimed and shot the arrow at him. Before that, I did not forget to fit the wooden shaft of the arrow. As soon as the arrow struck, he fell down and his legs went up. Seeing this, the Prophet (peace and blessings be upon him) laughed so much that his blessed teeth became visible. I asked the reason for this, and he replied: "Because of that man's action."