إِنَّ اللَّهَ لَا يَغْفِرُ أَنْ يُشْرَكَ بِهِ وَيَغْفِرُ مَا دُونَ ذَٰلِكَ لِمَنْ يَشَاءُ
Allah does not forgive association with Him, but forgives what is less than that for whom He wills.
A Muslim who commits a major sin and dies upon tawḥīd is not declared an unbeliever merely for that sin. Repentance, divine will, grace, and justice remain relevant to the case.
Committing a sin while recognizing its prohibition differs from declaring it lawful. The question of declaring prohibited things lawful must not be conflated with ordinary wrongdoing; neither may a person claim certain knowledge of another’s inward state or ending.