كتاب الْمَسَاجِدِ وَمَوَاضِعِ الصَّلاَةِ
5
The Book of Mosques and Places of Prayer
(4)
Chapter: The virtue of building masajid and encouragement to do so
(4)
باب فَضْلِ بِنَاءِ الْمَسَاجِدِ وَالْحَثِّ عَلَيْهَا ‏

Ubaidullah al-Khaulini reported:

'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."
حَدَّثَنِي هَارُونُ بْنُ سَعِيدٍ الأَيْلِيُّ، وَأَحْمَدُ بْنُ عِيسَى، قَالاَ حَدَّثَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي عَمْرٌو، أَنَّ بُكَيْرًا، حَدَّثَهُ أَنَّ عَاصِمَ بْنَ عُمَرَ بْنِ قَتَادَةَ حَدَّثَهُ أَنَّهُ، سَمِعَ عُبَيْدَ اللَّهِ الْخَوْلاَنِيَّ، يَذْكُرُ أَنَّهُ سَمِعَ عُثْمَانَ بْنَ عَفَّانَ، عِنْدَ قَوْلِ النَّاسِ فِيهِ حِينَ بَنَى مَسْجِدَ الرَّسُولِ صلى الله عليه وسلم ‏.‏ إِنَّكُمْ قَدْ أَكْثَرْتُمْ وَإِنِّي سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم 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 ‏"‏ ‏.‏
Reference : Sahih Muslim 533 a
In-book reference : Book 5, Hadith 29
USC-MSA web (English) reference : Book 4, Hadith 1084
  (deprecated numbering scheme)