Seven Arabic words repeated by every Muslim describe the very core of Islam. “Ilaha illa Allah. Muhammad rasul Allah.” (Important: see note below) “There is no God but God. Muhammad is the messenger of God.” This is the shahada, the great confession. (Quran 3:81; 5-83-84; 2:255; 3:18; 3:144; 4:87; 7:172; 33:40; 48:29; 64:8). It is said that to say those words and believe them is conversion to Islam and is what makes a Muslims a Muslim.
These words of the shahada are whispered into a Muslim’s ears at birth and at death. This confession is uttered fourteen times daily in the stated prayers. Muslims confess their monotheistic faith and their final prophet.
There are no other gods. Allah is God. God is creator, sustainers, and Lord. Muslims are accountable only to him. There were other prophets. But Muhammad is the last and final prophet.
Muslims honor and follow the life of Muhammad, both his public and private life. Thus, the confession provides the road map for life. Belief and practice fit together in submission to God and acknowledgement of the example of the final prophet. It unites the vertical and the horizontal, the spiritual and the ethical. God is the focus of worship and prayer. Muhammad is the role model for the individual and the community.
– Source: What You Need to Know About Islam & Muslims By George W. Braswell, Jr. Broadman & Holman Publishers, Nashville, Tennessee. 2000. Page 32
Note: In his review of What You Need To Know About Islam & Muslims, Rev. Bassam M. Madany notes:
On page 32, when transliterating the Arabic words of THE GREAT CREED OF ISLAM, an important word is omitted. The Arabic version "of the confession (shahada) of Muslims" is rendered: "Ilaha illa Allah. Muhammad rasul Allah."
The first Arabic word "La" of the confession is omitted. Without it (a negative particle,) the confession is meaningless. Usually, this brief Islamic credo is prefaced by the Arabic words: "Ash-hadu anna," i.e., I bear witness. The complete Muslim confession states: "La Ilaha illa Allah, Muhammad rasul Allah." ("I bear witness that there is no god but God, and Muhammad is the messenger of God."
– Source: Review: What You Need To Know About Islam & Muslims Reviewed by Rev. Bassam M. Madany, Calvin Theological Journal