Narrated Abu Sa'eed:
that the Messenger of Allah (ﷺ) said: "When you see a man frequenting the Masjid, then testify to his faith. Indeed Allah, Most High, said: The Masjid shall be maintained by those who believe in Allah and the Last day (9:18)." (DE)
English reference (DE): Vol. 5, Book 44, Hadith 3093 (DE)
Arabic reference (DE): Book 47, Hadith 3375 (DE)