وَوَقَعَ ٱلْقَوْلُ عَلَيْهِم بِمَا ظَلَمُوا۟ فَهُمْ لَا يَنطِقُونَ
Commentary:
The expression "they will be speechless" means, "they will not be able to put in a defence for their misdeeds." The charge against them being quite true and clear will be incapable of being defended and so the sentence of punishment will be passed against them.
They will not be able to put in defence of their misdeeds. The charge against them being quite true and manifest will be incapable of being defended, and so the sentence of punishment will be passed against them.