The Book Pertaining to Piety and Softening of Hearts (Kitab Al-Zuhd wa Al-Raqa'iq)
Muslim :: Book 42 : Hadith 7110
Mahmud b. Labid reported that 'Uthman b. 'Affan decided to rebuild the mosque (of Allah's Apostle in Medina) but the people did not like this idea and they wished that it should be preserved in the same (old) form. Thereupon he (Hadrat 'Uthman) said: I heard Allah's Messenger (may peace be upon him) as saying: He who builds a mosque for Allah, Allah would build for him (a house) in Paradise like it.