﴿ فَإِنْ أَعْرَضُوا۟ فَقُلْ أَنذَرْتُكُمْ صَٰعِقَةًۭ مِّثْلَ صَٰعِقَةِ عَادٍۢ وَثَمُودَ ﴾

“BUT IF they turn away, say: “I warn you of [the coming of] a thunderbolt of punishment like the thunderbolt [that fell upon the tribes] of Ad and Thamud!””

But if they that is the Meccan disbelievers turn away from belief after this clear statement then say ‘I warn you of I threaten you with a thunderbolt like the thunderbolt of ‘Ād and Thamūd’ in other words a chastisement that will destroy you like the one that destroyed them.