The Book of Zuhd and Softening of Hearts
Ṣaḥīḥ Muslim 7470
مَنْ بَنَى مَسْجِدًا - قَالَ بُكَيْرٌ حَسِبْتُ أَنَّهُ قَالَ - يَبْتَغِي بِهِ وَجْهَ اللَّهِ بَنَى اللَّهُ لَهُ مِثْلَهُ فِي الْجَنَّةِ
man banā masjidan-qāla bukayrun ḥasibtu annah qāla-yabtaghī bihi wajha-Llāh banā-Llāh lah mithlah fī al-jannah
Transliteration generated from the Arabic vowel marks
The full narration
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
Source
Ṣaḥīḥ Muslim · 7470