Hadith #2616 (Jami' al-Tirmidhi)
Book: The Book on Faith
Narrator(s): Ahmed bin Manay' أحمد بن منيع, Ali bin Ms'd'h al-Bahly علي بن مسعدة الباهلي أبو حبيب البصري, Anas ibn Malik, Qatada قتادة, Zayd bin al-Habab al-'Akli زيد بن الحباب أبو الحسين العكلي

that the Messenger of Allah (ﷺ) said: “If you see a man who comes to the Masjid then bear witness to his faith.” Because Allah, the Exalted, says: Only those who believe in Allah, and the Last Day, and establish the Salat, and give the Zakat (should) maintain the Masajid until the end of the Ayah (9:18)

Source: https://parallelquran.com/hadith/jami-al-tirmidhi-2616/