I heard the Messenger of Allah ﷺ say, "Whoever builds a masjid for Allah , Allah will build for him one like it in Paradise."
حدثنا عبد الكبير بن عبد المجيد أبو بكر الحنفي حدثنا عبد الحميد يعني ابن جعفر عن أبيه عن محمود بن لبيد عن عثمان بن عفان رضي الله عنه قال سمعت رسول الله ﷺ يقول من بنى مسجدا لله عز وجل بنى الله له مثله في الجنة
Its isnad is sahih. Abdul-Hameed bin Jafar Ansari is trustworthy. His father, Jafar bin Abdullah bin Hakam Ansari, is also trustworthy. Mahmud bin Labeed was one of the younger companions according to the correct view, and he was thirteen years old when the Messenger of Allah passed away. This will come at greater length in 506.