The Quran 12:40 (Surah Yusuf)
You worship not besides Him except (mere) names you have named them, you and your fathers, for which Allah has sent down no authority. Legislation is not but for Allah . He has commanded that you worship not except Him. That is the correct religion, but most of the people do not know.
Background Image: Masjid in the Taj Mahal complex in India, commissioned by Emperor Shah Jahan
