13فَإِن أَعرَضوا فَقُل أَنذَرتُكُم صاعِقَةً مِثلَ صاعِقَةِ عادٍ وَثَمودَMuhammad AsadBUT IF they turn away,1 say: "I warn you of [the coming of] a thunderbolt of punishment2 like the thunderbolt [that fell upon the tribes] of 'Ad and Thamud!"3This connects with the opening sentence of verse 9 above: "Would you indeed deny Him who has created...", etc.See note 40 on 2:55.For the story of these two ancient tribes, see 7:65-79 and the corresponding notes, in particular 48 and 56; also 26:123-158.