﴿ قُل لِّلَّذِينَ كَفَرُوٓا۟ إِن يَنتَهُوا۟ يُغْفَرْ لَهُم مَّا قَدْ سَلَفَ وَإِن يَعُودُوا۟ فَقَدْ مَضَتْ سُنَّتُ ٱلْأَوَّلِينَ ﴾

“Tell those who are bent on denying the truth that if they desist, all that is past shall be forgiven them; but if they revert [to their wrongdoing], let them remember what happened to the like of them in times gone by.”

Appearing once again in verse 38, there is a patronizing address to disbelievers - which carries the elements of persuasion and warning both. The part of persuasion is that should they repent from their shocking deeds even then, and come forward to believe, then, all their past sins shall be forgiven. If they failed to desist even then, the warning part tells them that they better understand that Allah Ta` ala would not have to think about making some new law for them. The law is already there. It has been in force in the case of disbelievers of earlier times. The same law would come into force against them too - that they were destroyed in the present world and became deserving of the punishment of the Hereafter.