It is narrated from Sayyiduna Ali (may Allah be pleased with him); he said: When the fighting grew fierce and the two armies met face to face, we would take shelter behind the Messenger of Allah (peace and blessings be upon him) (to protect ourselves from the enemy's attacks), and none of us would be as close to the enemy as the Messenger of Allah (peace and blessings be upon him) was (because of his courage). This hadith has a sahih (authentic) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.