( ذَٰلِكَ ) (That is): A reference to what preceded , and what proceeded is the misguidance which they took instead of guidance, the torment they took instead of forgiveness and the fire they will be tortured in while being patient on it . Hence, there are three connected elements mentioned here: Torment, misguidance and fire.
For misguidance is the main cause of the torment. When Allah (swt) says that they are punished with so and so because they have gone astray, then it is certainly true and when He (swt) says that they are punished with so and so of torture because they deserved it then He (swt) is certainly sincere. Torment in the Hereafter is with Hell’s fire, accordingly when Allah (swt) mentions that they are punished with fire or torment or misguidance, they all refer to one thing.
( ذَٰلِكَ بِأَنَّ اللَّهَ نَزَّلَ الْكِتَابَ بِالْحَقِّ ) (That is [deserved by them] because Allah has sent down the Book in truth): The one who changes the book and conceals it is the one who hates the truth.
( وَإِنَّ الَّذِينَ اخْتَلَفُوا فِي الْكِتَابِ لَفِي شِقَاقٍ بَعِيدٍ ) (And indeed, those who differ over the Book are in extreme dissension): It is a wide gap in which they fall. Schism in the heavenly methodology values means falling into a deep gap that has no end, since if the dispute is about material things, it would be possible for humans to tolerate from each other but the dispute in an issue of values, human beings cannot fix among them. Hence, the disagreement is wide, and cannot be governed except by Allah (swt).