Warning and preaching (da'wah)

إِنَّآ أَرْسَلْنَا نُوحًا إِلَىٰ قَوْمِهِۦٓ أَنْ أَنذِرْ قَوْمَكَ مِن قَبْلِ أَن يَأْتِيَهُمْ عَذَابٌ أَلِيمٌ

Indeed, We sent Noah to his people, [saying], "Warn your people before there comes to them a painful punishment."