Our beloved Prophet ﷺ said, “Whoever builds a mosque for Allah, Allah will build for him a house like it in Paradise.” (Bukhari) and in another narration said, "Whoever builds a mosque for the sake of Allah, like a sparrow's nest for Allah or even smaller, Allah will build for him a house in Paradise." (Ibn Majah)Source: al-Muʻjam al-Awsaṭ 6/139 Grade: Sahih (authentic)