Associating partners with Allah is called Shirk. Shirk is the worship of idols, and offering prayers and supplications to anyone, dead or living, believing that they hold the same attributes in a lesser degree than Him. Thus, the belief that Allah is not Sovereign or Independent and Sole Dispenser of affairs of the world and that other deities can intercede with Him is Shirk. To implore any other being besides Allah to grant any wishes or answer prayers is also Shirk. The Quran considers Shirk to be an unpardonable sin. It says:
“Allah forgives not that partners should be set up with Him; but He forgives anything else to whom He pleases; to set up partners with Allah is to devise a sin most heinous indeed.” (4: 48)
Man has been created as lord of creation and everything in nature has been placed under his control. By worshipping other beings besides Allah man debases himself. The Quran says:
“Shall I seek for you a God other than the ( true) God, when it is Allah who hath endowed you with gifts above the nation.” (7:140)
  The Holy Prophet PBUH is reported to have said: “Shirk is the Greatest of all sins.”