Bishr bin Hayyan narrates that Sayyiduna Wathilah bin al-Asqa' (may Allah be pleased with him) came to us while we were building a mosque. He stopped by us, greeted us with salam, then said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever builds a mosque for Allah in which prayer is offered, Allah will build for him a house in Paradise better than it."
Hadith Referenceالمعجم الكبير للطبراني / باب الواو / 18433