Quran 4:18 from Surah An-Nisaa on Divine Marvels.
وَلَيۡسَتِ ٱلتَّوۡبَةُ لِلَّذِينَ يَعۡمَلُونَ ٱلسَّيِّـَٔاتِ حَتَّىٰٓ إِذَا حَضَرَ أَحَدَهُمُ ٱلۡمَوۡتُ قَالَ إِنِّي تُبۡتُ ٱلۡـَٰٔنَ وَلَا ٱلَّذِينَ يَمُوتُونَ وَهُمۡ كُفَّارٌۚ أُوْلَٰٓئِكَ أَعۡتَدۡنَا لَهُمۡ عَذَابًا أَلِيمٗا
English translation: And not (is) the acceptance of repentance for those who do the evil deeds until when approaches one of them [the] death he says Indeed I repent now and not those who die while they (are) disbelievers Those We have prepared for them a punishment painful
Transliteration: walaysati al-tawbatu lilladhina ya'maluna al-sayiati hatta idha hadara ahadahumu al-mawtu qala inni tub'tu al-ana wala alladhina yamutuna wahum kuffarun ulaika a'tadna lahum adhaban aliman