فَكَيْفَ إِذَا جَمَعْنَاهُمْ لِيَوْمٍ لاَّ رَيْبَ فِيهِHow (will it be) when We gather them together on the Day about which there is no doubt (i. e. the Day of Resurrection).meaning, what will their condition be like after they have uttered this lie about Allah, rejected His Messengers and killed His Prophets and their scholars who enjoined righteousness and forbade evil Allah will ask them about all this and punish them for what they have done.This is why Allah said, فَكَيْفَ إِذَا جَمَعْنَاهُمْ لِيَوْمٍ لاَّ رَيْبَ فِيهِ (How (will it be) when We gather them together on the Day about which there is no doubt.) meaning, there is no doubt that this Day will come,وَوُفِّيَتْ كُلُّ نَفْسٍ مَّا كَسَبَتْ وَهُمْ لَا يُظْلَمُونَAnd each person will be paid in full what he has earned And they will not be dealt with unjustly.