Abu Maysarah (may Allah have mercy on him) narrates: Sayyiduna Sa'd (may Allah be pleased with him) said to the Messenger of Allah (peace and blessings be upon him): "I saw Ayman fleeing from the fighting", and I sensed displeasure on the face of the Messenger of Allah (peace and blessings be upon him). Sa'd (may Allah be pleased with him) said: I said: "I have never seen a remark so far removed from all good." Then, after that, when they faced the fighting, Sa'd (may Allah be pleased with him) said: "I saw Ayman fighting against the enemy with great valour", and this greatly pleased the Prophet (peace and blessings be upon him). Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) said to Ayman: "I have been told that you do not stand between the two ranks out of cowardice." He said: "I hope that I will stand in a position that Allah and His Messenger love." Sayyiduna Umar (may Allah be pleased with him) said: "You are indeed worthy of doing so."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 843