Quran 3:90 — The Amramites (Ali-'Imran)

إِنَّ الَّذينَ كَفَروا بَعدَ إيمٰنِهِم ثُمَّ ازدادوا كُفرًا لَن تُقبَلَ تَوبَتُهُم وَأُولٰئِكَ هُمُ الضّالّونَ

Those who disbelieve after believing, then plunge deeper into disbelief, their repentance will not be accepted from them; they are the real strayers.

[3:89] Exempted are those who repent thereafter, and reform. GOD is Forgiver, Most Merciful.

[3:91] Those who disbelieve and die as disbelievers, an earthful of gold will not be accepted from any of them, even if such a ransom were possible. They have incurred painful retribution; they will have no helpers.