Musnad Ahmad 3:108

Ad-Dahhak ibn Makhlad narrated to us, Abd al-Hamid ibn Ja'far narrated to us, my father narrated to me, from Mahmud ibn Labid: That Uthman wanted to rebuild the Mosque of Medina, but the people disliked that and preferred that he leave it in its state. Uthman said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Whoever builds a mosque for Allah, Allah will build for him a house in Paradise like it."