I heard the Messenger of Allah ﷺ say, "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 will have a reward like his until he dies or returns. And whoever builds a mosque for Allah in which Allah's name is mentioned, Allah will build for him a house in Paradise."
سمعت رسول الله ﷺ يقول: من أظل رأس غاز أظله الله يوم القيامة، ومن جهز غازيا حتى يستقل كان له مثل أجره حتى يموت، أو يرجع، ومن بنى لله مسجدا يذكر فيه اسم الله تعالى، بنى الله له به بيتا في الجنة.
Ahmad (136), Ibn Majah (735, 2758), Ibn Abu Shayba (19902), and Hakim (2/89) all narrated it through various chains from Layth bin Saad, from Yazid bin Abdullah bin Usama bin Hadd, from Walid bin Abu Walid, from Uthman bin Abdullah bin Suraqa, from Umar bin Khattab, who related it. The wording given is that of Ahmad, and some of them narrated it in abbreviated form. Hakim said, "This is a hadith sahih in isnad." I say, it is as he said, and the discussion of this isnad is treated at length in the chapter on the merit of building a masjid.