Quran 4:18 An-Nisa, ayah 18 of 176

وَلَيْسَتِ ٱلتَّوْبَةُ لِلَّذِينَ يَعْمَلُونَ ٱلسَّيِّـَٔاتِ حَتَّىٰٓ إِذَا حَضَرَ أَحَدَهُمُ ٱلْمَوْتُ قَالَ إِنِّى تُبْتُ ٱلْـَٔـٰنَ وَلَا ٱلَّذِينَ يَمُوتُونَ وَهُمْ كُفَّارٌ ۚ أُو۟لَـٰٓئِكَ أَعْتَدْنَا لَهُمْ عَذَابًا أَلِيمًا ۝١٨

4:18 The forgiveness is not for those who do ill-deeds until, when death attendeth upon one of them, he saith: Lo! I repent now; nor yet for those who die while they are disbelievers. For such We have prepared a painful doom.