Surah An-Nisa' (The Women), Verse 18

وَلَیْسَتِ التَّوْبَةُ لِلَّذِیْنَ یَعْمَلُوْنَ السَّیِّاٰتِ حَتّٰۤی اِذَا حَضَرَ اَحَدَهُمُ الْمَوْتُ قَالَ اِنِّیْ تُبْتُ الْـٰٔنَ وَلَا الَّذِیْنَ یَمُوْتُوْنَ وَهُمْ كُفَّارٌ اُولٰٓىِٕكَ اَعْتَدْنَا لَهُمْ عَذَابًا اَلِیْمًا ۟

Wa laisatit tawbatu lillazeena ya'maloonas saiyiaati hattaaa izaa hadara ahadahumul mawtu qaala innee tubtul 'aana wa lallazeena yamootoona wa hum kuffaar; ulaaa'ika a'tadnaa lahum 'azaaban aleemaa

“Of no effect is the repentance of those who continue to do evil, until death faces one of them, and he says, "Now have I repented indeed;" nor of those who die rejecting Faith: for them have We prepared a punishment most grievous.”

Quran 4:18 (Yusuf Ali Translation)