ENOfficial
Abu Sa'id al-Khudri reported God’s Messenger as saying, “When you see a man frequenting the mosque, testify that he has faith, for God says, ‘God’s mosques are visited only by those who believe in God and the last day.”* * Al-Qur'an; 9:18 Tirmidhi, Ibn Majah and Darimi transmitted it.
Source: sunnah.com
Other translations
Arabic
عَنْ أَبِي سَعِيدٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: " إِذَا رَأَيْتُمُ الرَّجُلَ يَتَعَاهَدُ الْمَسْجِد فَاشْهَدُوا لَهُ بِالْإِيمَان فَإِن الله تَعَالَى يَقُولُ (إِنَّمَا يَعْمُرُ مَسَاجِدَ اللَّهِ مَنْ آمَنَ بِاللَّه وَالْيَوْم الآخر وَأقَام الصَّلَاة وَآتى الزَّكَاة) رَوَاهُ التِّرْمِذِيّ وَابْن مَاجَه والدارمي
sunnah.com