If a Muslim fails to follow teachings of Muhammad can they rightly be called Muslims. In a similar way there is a huge gulf between nominal and genuine Christians.
The principal teaching of Islām, for utter simplicity, is what is known as the shahādah, or confession of faith, which every Muslim knows by heart: “La ilāh illa Allāh; Muḥammad rasūl Allāh” (No god but Allah; Muḥammad is the messenger of Allah). This agrees with the Qurʼānic expression, “Your God is One God; there is no God save Him, the Beneficent, the Merciful.” (Surah 2:163, MMP) This thought was stated 2,000 years earlier with the ancient call to Israel: “Listen, O Israel: Jehovah our God is one Jehovah.” (Deuteronomy 6:4) Jesus repeated this foremost command, which is recorded at Mark 12:29, about 600 years before Muḥammad, and nowhere did Jesus claim to be God or to be equal to Him.—Mark 13:32; John 14:28; 1 Corinthians 15:28.
