Imam Muslim rahimahullah narratedin his Sahih:
عَنْ عُثْمَانِ بْنَ عَفَّانَ قَالَ سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُعَلَيْهِ وَسَلَّمَ يَقُولُ مَنْ بَنَى مَسْجِدًا لِلَّهِ بَنَى اللَّهُ لَهُ فِي الْجَنَّةِ مِثْلَه
From Utsman bin Affan -radhiyallahu'anhu- he said; I heard the Prophet sallallaahu 'alaihi wa sallam said, "Whoever builds a mosque is sincere because of Allah then God will make him like him in heaven." (Narrated by Muslim in Kitab al-Masajid wa Mawadhi' as-Shalah)
