وَلِلْكَافِرِينَ أَمْثَالُهَا (And [ ready ] for [ these ] disbelievers are the likes thereof. - 47:10). Grammatically, the article "alif lam" in al-kafirina" in this context is used to indicate some specific disbelievers, and refers to the infidels of Makkah. The purpose of this sentence is to warn them: as the previous generations were punished for their iniquity, so will you meet similar fate for your iniquitous behavior. Do not be unconcerned!