Musnad Ahmad 2:294

Hassan ibn Musa al-Ashyab narrated to us, Ibn Lahi'ah narrated to us, al-Walid ibn Abi al-Walid narrated to us, from Uthman ibn Abdullah ibn Suraqah al-Adawi, from Umar ibn al-Khattab, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever shades the head of a warrior, Allah will shade him on the Day of Resurrection. Whoever equips a warrior until he is fully prepared with his equipment, he shall have the like of his reward. And whoever builds a mosque in which the name of Allah is mentioned, Allah will build for him a house in Paradise."