This statement of faith should be declared publicly. It should be a genuine belief which includes all the articles of faith. The witnessing of the Oneness of Allah is the rejection of any form of deity other than Allah, and the witnessing that Muhammad is His Messenger is the acceptance of him being chosen by Allah to convey His message of Islam to all humanity and to deliver it from the darkness of ignorance into the light of belief in, and knowledge of, the Creator.
The second phrase of the Shahada declares that Muhammad is God's messenger to humankind. Accepting the Judaeo-Christian Biblical tradition in large part, Muslims believe that God had sent prophets and messengers to other nations in the past with the same revealed message Muhammad was to recite to the Arabs. Muhammad's mission brought the final positing of divine Truth, and thus Muhammad is regarded as the "Seal of the Prophets."
Reciting and accepting the Shahadah, before two witnesses is all the formality required from new embracers of Islam. It is also included in the call to prayer (adhan) and repeated during all prayers. And yet it is more than a verbal formality, for when you take God as your God it means that you take Him as the shaper and guider of your life, undistracted by other influences be they people, things or moods and desires. And as you profess that Mohammad is His messenger it means a pledge to abide by the instructions and teachings given by Mohammad and to acknowledge their divine source. In Islamic jurisprudence and literature over the ages lengthy works have be written on the far reaching implications of 'No god but God and Mohammad is His messenger.'
Ashhadu Alla Ilaha Illa Allah Wa Ashhadu Anna Muhammadun rasulu'Llah
Which can be interpretation as: