Al Shu‘arā’

فَلاَ تَدْعُ مَعَ اللَّهِ إِلَهًا آخَرَ فَتَكُونَ مِنَ الْمُعَذَّبِينَ

213. “So call you not upon another god with Allah, lest you will be one of the chastised (ones).”

Allah prohibits the Prophet (S) from polytheism so that we learn; else, the Prophet (S) never sought other than Allah, even for a moment. The leaders of monotheism must themselves be the first monotheists; and whatever and whoever is besides Allah is not worthy of worshipping. Going towards anything other than Allah brings misery and chastisement in its sequel. It has been the cause of destruction of the former nations. Then, in this verse, before anything else, Allah invites the prophet (S) to having a firm belief in-Monotheism, a monotheism that formed the root and basis of the call of all prophets.

It says:

The Prophet of Islam (S) was certainly the herald of Monotheism and there was no deviation from this principle considered in him, yet the importance of this issue was so much that, at first He addresses him concerning this matter, in order that other persons settle their account. Besides that, improving others must begin by means of self-actualization and self-improvement.