وَلَقَد يَسَّرنَا القُرآنَ لِلذِّكرِ فَهَل مِن مُدَّكِرٍ

Certainly We have made the Quran simple for the sake of admonishment. So is there anyone who will be admonished?

EXEGESIS

This verse is repeated throughout this chapter after the story of each nation, to emphasise that these stories have been mentioned for a purpose: so that man may take admonition from them.

See verse 17 for a more detailed explanation of this verse.