Question: Who will have a worse punishment (in the Hereafter): The sinners or the innovators?
Response: The innovators will have a worse punishment, since innovation is worse than sin.
Innovations are more beloved to the Devil than sins because (it is likely) the sinner may repent, but as for the innovator, then very rarely does he repent because he thinks that he is upon the truth.
This is contrary to the sinner for he knows that he is disobeying Allaah and that he is committing a sinful deed.
As for the innovator, he considers himself to be obeying Allaah and to be upon obedience.
This is why innovation – and Allaah’s refuge is sought – is worse than sin.
And this is why the (Pious) Predecessors warned the people from sitting and gathering with the innovators for they would influence those whom they sat with, and their danger is great.
There is no doubt that innovation is worse than sin and that the danger of the innovator is worse to the people than the danger of the sinner.
Due to this, the (Pious) Predecessors would say: “Being moderate while upon the Sunnah is better than exerting oneself while upon Innovation.”
Shaykh Saalih ibn Fowzaan - a translation of al-Ajwibah al-Mufeedah ‘an As.ilatil-Manaahij al-Jadeedah via westlondondawah archive#512
