And He destroyed the overthrown cities.meaning, the cities (of Sodom and Gomorrah) to which Prophet Lut was sent. Allah turned their cities upside down over them and sent on them stones of Sijjil.Allah's statement that whatever has covered it, has covered it, is like the case with the stones of Sijjil that He sent on them,وَأَمْطَرْنَا عَلَيْهِم مَّطَراً فَسَأءَ مَطَرُ الْمُنذَرِينَAnd We rained on them a rain (of torment). And how evil was the rain of those who had been warned! (26:173)فَغَشَّاهَا مَا غَشَّى