Musnad Ahmad 132:35

Hassan narrated to us, Ibn Lahi'ah narrated to us, Zabban narrated to us, from Sahl ibn Mu'adh, from his father, from the Messenger of Allah (peace and blessings of Allah be upon him) that he said: "For me to see off a mujahid in the way of Allah, and to assist him in mounting his riding beast in the morning or in the evening, is more beloved to me than the world and what is in it."