Question: Does committing a major sin leave any room for repentance and mercy?
Answer: Yes. Serious sin remains serious, but repentance and hope in divine mercy remain open. The fate of sinful monotheists rests under Allah’s justice and grace; eternal punishment is not automatically assigned to every major sinner.
وَأَهْلُ الْكَبَائِرِ مِنْ أُمَّةِ مُحَمَّدٍ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي النَّارِ لَا يُخَلَّدُونَ إِذَا مَاتُوا وَهُمْ مُوَحِّدُونَ
Major sinners of the Muhammadan community do not remain eternally in the Fire if they die as monotheists.
Follow-up: Does such hope make the commission of sin harmless?
Clarification: No. Hope goes with fear, repentance, restoring rights and reforming conduct; mercy cannot be turned into permission to sin.