Associating partners with Allah is a great form of wrongdoing. In particular, one is completely wronging one’s own soul and dignity by submitting to and worshiping beings that do not deserve a human’s worship whatsoever. Allah has stated in the Quran, while quoting Luqmaan, “Indeed associating [partners with Allah] is a great wrongdoing” (31:13). Thus, Allah has said in the Quran, “O believers! Verily, the polytheists are impure” (9:28). This is a spiritual impurity, illustrating that one is denigrating one’s soul.
Once the concept of pure monotheism is truly understood and embodied in a person, there is a certain type of nobility (for lack of a better word) and feeling of purpose that accompanies the soul. The person realizes that he is not to submit to, physically bow down or prostrate to anything or anyone other than Allah. He does not turn in his prayers to anyone other than Allah, nor can anyone grant him forgiveness save Allah. He does not turn to dead humans who, in reality, were no more than humans themselves. He does not sit at the base of wooden or metal idols that other humans themselves actually created. He does not fear any form of spirits such that he has to appease them by offering sacrifices to them. Furthermore, such a person will base his life on his belief in there being only one true God.
All of these things are forbidden to him by the concept of monotheism. But they are more than simply forbidden for him. He understands full well that all of these acts are not becoming a human being that Allah has created for a very special and noble purpose. All of these acts are beneath a human and, in fact, it is inconceivable that a person who has a sane understanding of reality would ever take part in those types of acts. Why should a human bow down and pray to another human who has to eat and drink to survive just like himself? How could anyone claim that another being has any share in the divinity with Allah and therefore is deserving of having others humble and prostrate themselves before him?