إِن

وَإِن كَانُوا۟ لَيَقُولُونَ

And indeed, they [i.e., the disbelievers] used to say,

أَفَرَءَيْتَ إِن مَّتَّعْنَـٰهُمْ سِنِينَ

Then have you considered if We gave them enjoyment for years

إِنْ أَنتَ إِلَّا نَذِيرٌ

You, [O Muḥammad], are not but a warner.