"Say, 'Have you considered if it is from Allah,'" meaning: the Quran, "'then you disbelieved in it, who is more astray than he who is in dissent,'" meaning: in separation from the Prophet and what he brought, "'far away'" from the truth, meaning: no one is more astray than him.
﴿قُلْ أَرَأَيْتُمْ إِنْ كَانَ مِنْ عِنْد الله﴾ يَعْنِي: الْقُرْآن ﴿ثُمَّ كَفَرْتُمْ بِهِ مَنْ أَضَلُّ مِمَّنْ هُوَ فِي شقَاق﴾ فِي فِرَاق للنَّبِي وَمَا جَاءَ بِهِ ﴿بعيد﴾ من الْحق , أَي: لَا أحد أضلّ مِنْهُ.