﴿ وَلَيْسَتِ ٱلتَّوْبَةُ لِلَّذِينَ يَعْمَلُونَ ٱلسَّيِّـَٔاتِ حَتَّىٰٓ إِذَا حَضَرَ أَحَدَهُمُ ٱلْمَوْتُ قَالَ إِنِّى تُبْتُ ٱلْـَٰٔنَ وَلَا ٱلَّذِينَ يَمُوتُونَ وَهُمْ كُفَّارٌ ۚ أُو۟لَٰٓئِكَ أَعْتَدْنَا لَهُمْ عَذَابًا أَلِيمًۭا ﴾

“whereas repentance shall not be accepted from those who do evil deeds until their dying hour and then say, "Behold, I now repent"; nor from those who die as deniers of the truth: it is these for whom We have readied grievous suffering.”

(The forgiveness) Allah overlooking sins (is not for those who do ill deeds until, when death attendeth upon one of them) when one of them is suffering from the agony of death, (he saith: Lo! I repent now; nor yet for those who die while they are disbelievers). Allah says that He does not accept the repentance of unbelievers at the moment they suffer the pangs of death. (For such) for the unbelievers (We have prepared a painful doom) this was revealed about Tu'mah and his companions who had left Islam.