Belief in one God, Allah in Arabic, constitutes the very foundation of Islam. There is no deity except Allah. He is indivisible and absolutely transcendent. God is the Almighty, the Creator and the Sustainer of the universe, Who is similar to nothing and nothing is comparable to Him.
The basic message of Islam is that God (Allah in Arabic) and His creation are distinctly different entities. Neither is Allah His creation or a part of it, nor is His creation Him or a part of Him. This might seem obvious, but, man's worship of creation instead of the Creator is to a large degree based on ignorance of this concept. It is the belief that the essence of Allah is everywhere in His creation or that His divine being is or was present in some aspects of His creation, which has provided justification for the worship of creation, though such worship may be called the worship of Allah through his creation.
However, the message of Islam as brought by the prophets of Allah is to worship only Allah and to avoid the worship of his creation either directly or indirectly.
(Read more: The True Religion)
Say: He is God, the One and Only; God, the Eternal, Absolute; He begets not, nor is He begotten; And there is none like unto Him. (Surah 112)
God is He, than Whom there is no other god;- Who knows (all things) both secret and open; He, Most Gracious, Most Merciful. God is He, than Whom there is no other god;- the Sovereign, the Holy One, the Source of Peace (and Perfection), the Guardian of Faith, the Preserver of Safety, the Exalted in Might, the Irresistible, the Supreme: Glory to God! (High is He) above the partners they attribute to Him.
He is God, the Creator, the Evolver, the Bestower of Forms (or Colors). To Him belong the Most Beautiful Names: whatever is in the heavens and on earth, doth declare His Praises and Glory: and He is the Exalted in Might, the Wise. (59:22-24)