Wa-ith qala luqmanu libnihi wahuwa yaAAithuhu ya bunayya la tushrik billahi inna (surah Luqman: 13)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(31:13) And call to mind when Luqman said to his son while exhorting him: 'My son, do not associate others with Allah in His Divinity. *20 Surely, associating others with Allah in His Divinity is a mighty wrong.' *21

Wa iz qaala luqmaanu libnihee wa huwa ya`izuhoo ya bunaiya laa tushrik billaah; innash shirka lazulmun `azeem

*20) This particular admonition from the wisdom of Luqman has been cited here for two reasons: (1) He gave this admonition to his son, and obviously, no one can be insincere to one's own children. A person may deceive others, may behave hypocritically towards them, but no one, not even a most depraved person, will try to deceive and defraud his own children. Therefore, Luqman's admonishing his son thus is a clear proof of the fact that in his sight shirk was indeed the most heinous sin, and for that very reason he first admonished his dear son to refrain from this iniquity. (2) The second reason for this narration is that many parents from among the disbelievers of Makkah were compelling their children to turn away from the message of Tauhid being preached by the Holy Prophet Muhammad (upon whom be Allah's peace) and remain steadfast on the creed of shirk, as is being stated in the following verses. Therefore, those foolish people are being told, as if to say, The well-known sage of your own land had wished his children well by admonishing thetas to avoid shirk, now you should judge it for yourself whether you arc wishing your children well or ill when you compel them to follow the same creed of shirk."
*21) Zulm means to deprive someone of his right and to act unjustly. Shirk is a grave iniquity because man sets up such beings as equals with his Creator and Providence and Benefactor as have no share whatever in creating him, nor in providing for him, nor in bestowing the blessings on him, which he is enjoying in the world. There could be no greater injustice than this. The Creator's right on man is that he should worship Him alone, but he worships others and so deprives Him of His right. Then, in whatever he does in connection with the worship of others than Allah, he exploits many things, from his own mind and body to the earth and heavens, whereas, all these things have been created by Allah, the One. and man has no right to use any of them in the worship of any other than Allah Then, the right of man's own self on him is that he should not debase and involve it in punishment. But when he worships others than his Creator. he debases his self as well as makes it deserving of the punishment. Thus, the entire life of a mushrik becomes Zulm in every aspect and at all times and his every breath becomes an expression of injustice and iniquity.