Surah Fussilat — Ayah 13 (41:13)
فَإِنۡ أَعۡرَضُواْ فَقُلۡ أَنذَرۡتُكُمۡ صَٰعِقَةٗ مِّثۡلَ صَٰعِقَةِ عَادٖ وَثَمُودَ ١٣
English translation (Saheeh International)
But if they turn away, then say, "I have warned you of a thunderbolt like the thunderbolt [that struck] ʿAad and Thamūd.
Brief commentary
So if these people turn away from bringing faith in what you have brought, then say to them: “I have warned you of a punishment that will fall upon you, like the punishment that fell upon the people of Hud, the ‘Ād, and the people of Saleh, the Thamūd, when they rejected their messengers.