Musnad Ahmad 2:45

Abu Salamah al-Khuza'i narrated to us, Layth and Yunus informed us, Layth narrated to us, from Yazid ibn Abdullah ibn Usamah ibn al-Had, from al-Walid ibn Abi al-Walid, from Uthman ibn Abdullah—meaning Ibn Suraqah—from Umar ibn al-Khattab, who said: I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: "Whoever shades the head of a warrior, Allah will shade him on the Day of Resurrection. And whoever equips a warrior until he departs, he shall have the like of his reward until he dies"—Yunus said: "or returns." And whoever builds a mosque for Allah in which the name of Allah the Exalted is mentioned, Allah will build for him a house in Paradise because of it.