'Uthman b. 'Affan listened to the opinion of the people (which was not favourable) when he rebuilt the mosque of the Messenger of Allah ﷺ. Thereupon he said: You have not been fair to me for I have heard from the Messenger of Allah ﷺ saying: He who built a mosque for Allah, the Exalted, Allah would build for him a house in Paradise. Bukair said: I think he (the Holy Prophet) said: While he seeks the pleasure of Allah (by building the mosque). And in the narration of Ibn 'Isa (the words are):" (a house) like that (mosque) in Paradise."  

أَنَّهُ سَمِعَ عُثْمَانَ بْنَ عَفَّانَ عِنْدَ قَوْلِ النَّاسِ فِيهِ حِينَ بَنَى مَسْجِدَ الرَّسُولِ ﷺ إِنَّكُمْ قَدْ أَكْثَرْتُمْ وَإِنِّي سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ مَنْ بَنَى مَسْجِدًا لِلَّهِ تَعَالَى قَالَ بُكَيْرٌ حَسِبْتُ أَنَّهُ قَالَ يَبْتَغِي بِهِ وَجْهَ اللَّهِ بَنَى اللَّهُ لَهُ بَيْتًا فِي الْجَنَّةِ وَقَالَ ابْنُ عِيسَى فِي رِوَايَتِهِ مِثْلَهُ فِي الْجَنَّةِ  

When 'Uthman b. 'Affan intended to build the mosque (of the Prophet) the people did not approve of it. They liked that it should be kept in the same state. Thereupon he said: I heard the Messenger of Allah ﷺ say: He who built a mosque for Allah, Allah would build a house for him like it in Paradise.  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ مَنْ بَنَى مَسْجِدًا لِلَّهِ بَنَى اللَّهُ لَهُ فِي الْجَنَّةِ مِثْلَهُ