Fussilat - 41:13

فَإِنْ أَعْرَضُوا فَقُلْ أَنذَرْتُكُمْ صَاعِقَةً مِّثْلَ صَاعِقَةِ عَادٍ وَثَمُودَ
[41:13]
But if they turn aside, then say: I have warned you of a scourge like the scourge of Ad and Samood.
But if they turn away, say thou: "I have warned you of a stunning Punishment (as of thunder and lightning) like that which (overtook) the 'Ad and the Thamud!"
But if they turn away, then say: I warn you of a thunderbolt like the thunderbolt (which fell of old upon the tribes) of A'ad and Thamud;