From Sahih Muslim (Hadith 7470):
Abdullah al-Khaulani reported that when Uthman b. 'Affan tried to rebuild the mosque of Allah's Messenger (ﷺ) the people began to talk about this. Uthman b. 'Affan said:You discuss it very much whereas I have heard Allah's Messenger (ﷺ) as saying: He who builds a mosque-- and the narrator Bukair said: I think he also said: (for) seeking the pleasure of Allah- Allah would build (a similar house for him in Paradise). and in the narration of Harun (the words are):" A house for him in Paradise
Reference: Muslim 7470