وَ رَأَى عَلِيٌّ ع مَسْجِداً بِالْكُوفَةِ قَدْ شُرِّفَ قَالَ كَأَنَّهُ بِيعَةٌ إِنَّ الْمَسَاجِدَ لَا تُشَرَّفُ تُبْنَى جُمّاً.
English translationBab Ul Qaim Publications
Hadith.708 - Imam Ali ibn Abi Talib (as) saw a mosque in Kufa that had been decorated or elevated and said: "It is as if it is a church. Mosques are not to be adorned; they should be built plain (simple)."
Translation: Bab Ul Qaim Publications·Thaqalayn link·The Arabic above is the original.