Tafsir of Az-Zumar 39:25

"Those before them denied": This is a resumption [of the narrative], introduced to explain the worldly torment that befell some of the disbelievers, following the explanation of the otherworldly torment that will befall them all. That is, those before them among the previous nations denied [the truth], so the torment—decreed for each of their nations—came upon them "from where they do not perceive"; meaning, from the direction they did not anticipate and from which the arrival of the torment did not cross their minds, for that is more severe upon the soul.