Al-Dhariyat (The Scattering Winds) Sura 51: Verses 56-58
"I have only created the invisible beings [jinn] and the human beings so that they may [know and] worship Me. No sustenance do I ever want from them, nor do I want them to feed Me. Surely, God is the Provider of all sustenance, the One with all might, the Ever-invulnerable"
God has His purpose and plan behind creation, which we may understand as giving all creatures the chance to fulfill their potentials through following the natural laws of the Creator. For human beings, this means following God's guidance and the human mind.
Rational beings accept the existence of God by using their minds, and this is the intentional and voluntary statement made by the "homo sapiens" which represents the essence of worship, ibada: the acknowledgement of the true and absolute Divinity and Supreme "Lordship" of the One God, and the true and full "submission" of the human being. This realization and reckoning lead the human being to conform to God's message and plan for the fulfillment of all the human internal and external potential, while the All-mighty Lord Himself is in no need of being acknowledged or worshiped, since He is self-sufficient, infinite in His power and free of all needs.
God is the source and centre of all power and all goodness, and human progress depends upon our aligning ourselves with His will in all creation in this world's life and His guidance as represented in His messages. This is the meaning and purpose of worshipping Him. Any power which we seek must be from God, whose power is eternal, universal and beyond any bias. His care and grace are always sure, but they are applied together with His justice. His providence in this life reaches those who believe in Him and those who reject Him, the good-doers and the evil-doers. In the end, every human individual will be accountable for all that he/she has done with what God has granted him/her.
"Concepts of the Quran" - Fathi Osman, p. 582