﴿ وَيَوْمَ يُعْرَضُ ٱلَّذِينَ كَفَرُوا۟ عَلَى ٱلنَّارِ أَلَيْسَ هَٰذَا بِٱلْحَقِّ ۖ قَالُوا۟ بَلَىٰ وَرَبِّنَا ۚ قَالَ فَذُوقُوا۟ ٱلْعَذَابَ بِمَا كُنتُمْ تَكْفُرُونَ ﴾

“And so, on the Day when those who were bent on denying the truth will be brought within sight of the fire [and will be asked], “Is not this the truth?” - they will answer, “Yea, by Our Sustainer!” [And] He will say: “Taste, then, this suffering as an outcome of your denial of the truth!””

یغْفِرْ‌ لَكُم مِّن ذُنُوبِكُمْ (will forgive your sins for you,) The word 'min' used in the text gives the sense of 'some'. If it is taken in this sense here, it would mean that 'some sins' will be forgiven by embracing Islam. It will indicate that only sins relating to the rights of Allah would be forgiven but not the rights of people. But some exegetes have taken 'min' in this verse as an extra word that has no additional meaning in Arabic idioms. Given this interpretation, no explanation is required.