Аль-Анам 6:64

Basically, polytheism (shirk) is the reposing of one’s faith in some entity other than God, while monotheism is directing of man’s entire faith solely towards God. One form of polytheism is that which involves worship of deities and of other phenomena. But exhibiting ingratitude instead of gratitude is also ‘shirk’. The more common form of shirk is that whereby a man makes a deity of himself; he starts having faith only in himself. When a man proves to be vain, it is as if he has faith in his efforts alone. When a man considers his earnings as actually having been generated by him, he in fact has faith only in his own talents. When a man overlooks another’s right, he thinks that nobody can inflict any punishment on him for doing so. When a man dares to oppress another, he thinks that he has full powers over the wronged person and there is nobody to prevent him from doing whatever he likes to him. All these are forms of vanity and pride. And pride is—before God—the worst type of shirk, because indulging in this amounts to placing oneself in the position of God.