Musnad Ahmad

Sayyiduna Iyad Ash'ari (may Allah be pleased with him) says: I was present at the Battle of Yarmouk. Five commanders were appointed over us: Abu Ubaidah ibn al-Jarrah, Yazid ibn Abi Sufyan, Ibn Hasnah, Khalid ibn Walid, and Iyad ibn Ghanm (note that this does not refer to the narrator of the hadith himself). Sayyiduna Umar (may Allah be pleased with him) had instructed that when the battle begins, your leader should be Sayyiduna Abu Ubaidah ibn al-Jarrah (may Allah be pleased with him). The narrator says: We wrote a letter to Sayyiduna Umar (may Allah be pleased with him) saying that death is leaping towards us, so send us reinforcements. He replied in writing: Your letter has reached me in which you requested help from me. I am telling you about such a Being whose help is the strongest and whose army is the most ever-present; that Being is Allah, the Blessed and Exalted. Seek help from Him, for the help of the Messenger of Allah (peace and blessings be upon him) was also granted at the Battle of Badr, even though they were much fewer in number than you. Therefore, when my letter reaches you, begin fighting them, and do not repeatedly ask me for help. The narrator says: Then we began fighting and inflicted a shameful defeat upon the polytheists, killing them for four farsakhs, and we also obtained spoils of war. After that, the Mujahideen consulted among themselves. Sayyiduna Iyad (may Allah be pleased with him) suggested that each Mujahid should be given ten dirhams per person. Sayyiduna Abu Ubaidah (may Allah be pleased with him) asked: Who will take care of this with me? A young man said: If you are not displeased, I will do it. Saying this, he went ahead. I saw the locks of Sayyiduna Abu Ubaidah's (may Allah be pleased with him) hair waving in the air, and that young man was riding behind him on an Arabian horse.