(Verily, Allah forgives not (the sin of) setting up partners (in worship) with Him, but He forgives whom He wills, sins other than that,) before and mentioned the relevant Hadiths in the beginning of this Surah. Allah's statement,
(and whoever sets up partners in worship with Allah, has indeed strayed far away.) means, he will have taken other than the true path, deviated from guidance and righteousness, destroyed himself in this life and the Hereafter, and lost contentment in this life and the Hereafter. Juwaybir said that Ad-Dahhak said about Allah's statement,
Though, the mention of Jihad in preceding verses includes all forces hostile to Islam, yet the actual description was limited to Jews and the hypocrites. Out of the larger group of antagonists there were the pagans who were much more in numbers. The verses that follow take up their beliefs and point out to the punishment they will face. This has a coherence of its own at this place. It will be recalled that the thief mentioned earlier became an apostate. The lasting punishment he thus earned for himself becomes evident. (Bayan a1-Qur'an)
Commentary
The first verse (116) إِنَّ اللَّـهَ لَا يَغْفِرُ أَن يُشْرَكَ بِهِ وَيَغْفِرُ مَا دُونَ ذَٰلِكَ لِمَن يَشَاءُ ۚ (Surely, Allah does not forgive the ascribing of a partner to Him and forgives anything short of that for whomsoever He wills ...) has appeared earlier (48) in Surah al-Nis-a' in the same words except for the words at their ends. In verse 48 appearing earlier, the words at the end are: وَمَن يُشْرِكْ بِاللَّـهِ فَقَدِ افْتَرَىٰ إِثْمًا عَظِيمًا whoever ascribes a partner to Allah has designed a great sin) while the words at the end of verse 116 before us are: وَمَن يُشْرِكْ بِاللَّـهِ فَقَدْ ضَلَّ ضَلَالًا بَعِيدًا (And whoever ascribes a partner to Allah has indeed gone far astray). As explained by master exegetes, the reason for this difference is that the addressees of the earlier verse (48) were the Jewish people of the Book who knew all about the truth of Tauhid (Allah's oneness), the falsity of Shirk (ascribing of a partner to Allah) and the veracity of the mission of the noble Prophet ﷺ through the Torah. Despite that, they got involved in Shirk. Thus, through their own conduct, they pretended that it was the very teaching of the Torah which is total forgery and false accusation. That is why it was said: فَقَدِ افْتَرَىٰ إِثْمًا عَظِيمًا (... has designed a great sin) at the end of verse 48. As for the verse before us (116), the addressees were the pagans of Makkah who did not have the background of any Book or Prophet before that time, but the rational arguments in support of the Oneness of Allah were all too clear. Taking stones crafted with their own hands as their objects of worship was something ineffectual, false and erroneous even in the sight of someone with ordinary common-sense. Therefore, here it was said: فَقَدْ ضَلَّ ضَلَالًا بَعِيدًا (... has indeed gone far astray).
Man’s real challenge in this world is from Satan. Though Satan has no real power, he can lure human beings with fanciful promises to fulfil wishful, imaginary desires and thus manage to make them deviate from the straight path of truth. Satan’s way of misguiding is of two main types: one is superstition and the other is interference in God’s creation. Faith in superstition means expectation of such results from something as have no relation with that thing.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.