The danger of ḍhulm (transgression) and shirk (association of partners in worship) with Him (Allāh) is that it destroys good deeds and it makes one enter hell fire forever, if a slave [of Allāh] dies upon that, refuge is sought in Allāh—the Mighty and Majestic—, we ask Allāh for wellness and safety.
And, it is prohibition from shirk in the book of Allāh—the Majestic and All-High— has been mentioned in many places, from the Fātiḥah (opening chapter) of the book to its nās(Surah an-Nās), from sūrah al-Fātiḥah to sūrah an-Nās. All of it commands lwith tawḥīd (monotheism) and prohibition from shirk, explains the station of the monotheists and their status with Allāh—the Mighty and Majestic— in the world and hereafter. And what He [Allāh] prepared for them of gardens, blessings and treasures and explains what Allāh—the Mighty and Majestic— prepared of detestable things, hell and punishment for the polytheists in the world, their graves and the hereafter in the hell fire, refuge is sought in Allāh.
The Qurʾān is all about tawḥīd, as Imām Ibn al-Qayyim, may Allāh have mercy on him, and other than him from the Imāms said. It [the Qurʾān] is all about the explanation of tawḥīd and what is related to it. Allāh—the Mighty and Majestic— said in His noble book:
﴾Worship Allāh and join none with Him (in worship)﴿ (Nisāʾ: 36)
And He—Majestic is His Mention— said:
﴾Say (O Muhammad ﷺ): “Come, I will recite what your Lord has prohibited you from: Join not anything in worship with Him﴿ [Anʿām: 151]
And He—Majestic is His Mention— said:
﴾And (remember) when We showed Ibrāhīm (Abraham) the site of the (Sacred) House (the Kaʿbah at Makkah) (saying): “Associate not anything (in worship) with Me”﴿ [Ḥajj: 26]
And Allāh—the Mighty and Majestic— said:
﴾Verily, Allāh forgives not that partners should be set up with Him (in worship), but He forgives except that (anything else) to whom He wills; and whoever sets up partners with Allāh in worship, he has indeed invented a tremendous sin.﴿ [Nisāʾ: 48]
﴾Verily! Allāh forgives not (the sin of) setting up partners (in worship) with Him, but He forgives whom He wills sins other than that, and whoever sets up partners in worship with Allāh, has indeed strayed far away.﴿ [Nisāʾ: 116]
And He—the Majestic and All-High— said:
﴾Do they attribute as partners to Allāh those who created nothing but they themselves are created?﴿ [Aʿrāf: 191]
And He—Majestic is His Mention— said:
﴾The Event (the Hour or the punishment of disbelievers and polytheists or the Islāmic laws or commandments) ordained by Allāh will come to pass, so seek not to hasten it. Glorified and Exalted be He above all that they associate as partners with Him.﴿ [Naḥl: 1]
And other than that from the very numerous verses about the explanation of tawḥīd and prohibition of shirk and tandīd (setting up partners with Allāh in worship).
And verily, Allāh—the Mighty and Majestic— praised His Prophets,, Messengers and His righteous slaves, for their adherence to tawḥīd and their warning from shirk and their abandoning it. Allāh narrated for us in what He narrated in Sūrah Yūsuf, his[Yūsuf] statement—May blessings and peace be upon him—
﴾”And I have followed the religion of my fathers, – Ibrāhīm (Abraham), Ishāq (Isaac) and Ya‘qūb (Jacob) [عليهم السلام], and never could we attribute any partners whatsoever to Allāh. This is from the Grace of Allāh to us and to mankind, but most men thank not (i.e. they neither believe in Allāh, nor worship Him).﴿ [Yūsuf: 38]
And when Allāh guided a few group of jinns to tawḥīd and sunnah, they warned their people from shirk and innovation. They said; as it is in sūrah al-Jinn:
﴾It guides to the right path﴿ [Jinn: 2]
They were describing the Book of Allāh—the Mighty and Majestic— and what they heard from the Prophet ﷺ.
﴾‘It guides to the Right Path, and we have believed therein, and we shall never join (in worship) anything with our Lord (Allāh).﴿ [Jinn: 2]
[i.e.,] “From today [on ward] we shall not join [in worship] anything with our Lord.”
[Meaning] “Naʿam, we used to be polytheists, then Allāh guided us to this noble Prophet to hear from him these great words [the Qurʾān], and they believed in Allāh—the All-Mighty All-Majestic— and they returned to their people as warners, they returned to their people, calling them to tawḥīd and sunnah and warning them from shirk, tandīd [making partners with Allāh in worship], innovations and transgressions.
﴾and we shall never join (in worship) anything with our Lord (Allāh).﴿ [Jinn: 2]
