Sahih Muslim 533
Sahih Muslim · Book 5: The Book of Mosques and Places of Prayer · The virtue of building masajid and encouragement to do so
Mahmud b. Labid reported:
حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ ، وَمُحَمَّدُ بْنُ الْمُثَنَّى ، - وَاللَّفْظُ لاِبْنِ الْمُثَنَّى - قَالاَ حَدَّثَنَا الضَّحَّاكُ بْنُ مَخْلَدٍ ، أَخْبَرَنَا عَبْدُ الْحَمِيدِ بْنُ جَعْفَرٍ ، حَدَّثَنِي أَبِي ، عَنْ مَحْمُودِ بْنِ لَبِيدٍ ، أَنَّ عُثْمَانَ بْنَ عَفَّانَ ، أَرَادَ بِنَاءَ الْمَسْجِدِ فَكَرِهَ النَّاسُ ذَلِكَ فَأَحَبُّوا أَنْ يَدَعَهُ عَلَى هَيْئَتِهِ فَقَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " مَنْ بَنَى مَسْجِدًا لِلَّهِ بَنَى اللَّهُ لَهُ فِي الْجَنَّةِ مِثْلَهُ " .
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.