Sunan Ibn Majah 736
سنن ابن ماجه#736SahihIt was narrated that 'Uthman bin 'Affan said:"I heard the Messenger of Allah say: 'Whoever builds a mosque for the sake of Allah, Allah will build something similar for him in Paradise
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Fouad Abd al-BaqiSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 4:2