Sunan At-Tirmidhi

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)."" (Another chain) from Abu Sa'eed from the Prophet (ﷺ) with similar wording except that he said: ""Yata'ahadul Masjid