Surah Fussilat Ayah #13 Translated in English
فَإِنْ أَعْرَضُوا فَقُلْ أَنْذَرْتُكُمْ صَاعِقَةً مِثْلَ صَاعِقَةِ عَادٍ وَثَمُودَ
But if they turn away, then say, "I have warned you of a thunderbolt like the thunderbolt [that struck] ʿAad and Thamūd.