فَارْتَقِبْfa-ir'taqibThen watchيَوْمَyawma(for the) Dayتَأْتِيtatī(when) will bringالسَّمَٓاءُl-samāuthe skyبِدُخَانٍbidukhāninsmokeمُب۪ينٍۙmubīninvisibleTherefore, watch for the day when the sky will bring a visible smoke/gas.