Surah 5. Al-Ma'ida, Ayah 40

Punishment really does not belong to mortals, but to Allah alone. Only, in order to keep civil society together, and protect innocent people from crime, certain principles are laid down on which people can build up their criminal law. But we must always remember that Allah not only punishes but forgives, and forgiveness is the attribute which is more prominently placed before us. It is not our wisdom that can really define the bounds of forgiveness or punishment, but His Will or Plan, which is the true standard of righteousness and justice.