Surah An-Nisa — Ayah 18 (4:18)
وَلَيۡسَتِ ٱلتَّوۡبَةُ لِلَّذِينَ يَعۡمَلُونَ ٱلسَّيِّـَٔاتِ حَتَّىٰٓ إِذَا حَضَرَ أَحَدَهُمُ ٱلۡمَوۡتُ قَالَ إِنِّي تُبۡتُ ٱلۡـَٰٔنَ وَلَا ٱلَّذِينَ يَمُوتُونَ وَهُمۡ كُفَّارٌۚ أُوْلَٰٓئِكَ أَعۡتَدۡنَا لَهُمۡ عَذَابًا أَلِيمٗا ١٨
English translation (Saheeh International)
But repentance is not [accepted] of those who [continue to] do evil deeds up until, when death comes to one of them, he says, "Indeed, I have repented now," or of those who die while they are disbelievers. For them We have prepared a painful punishment.
Brief commentary
Allah does not turn in mercy and forgiveness to those who continue in their disobedience, overstepping the limits and insisting on overstepping them, and not turning away from doing this until they are dying, then saying that they regret what they did and asking for Allah’s forgiveness. Also, Allah does not turn in mercy and forgiveness to those who die in disbelief – He has prepared a painful punishment for them.