إِنَّ رَبَّكَ هُوَ أَعْلَمُ بِمَن ضَلَّ عَن سَبِيلِهِ
(Truly, your Lord best knows who has strayed from His path,) meaning, Allah already knows who is doomed (destined for Hell) and who is blessed (destined for Paradise). This has already been written with Him and the matter is finished, so call them to Allah, but do not exhaust yourself with regret over those who go astray, for it is not your task to guide them. You are just a warner, and all you have to do is convey the Message, and it is He Who will bring them to account.