﴿ وَأَنذِرْهُمْ يَوْمَ ٱلْحَسْرَةِ إِذْ قُضِىَ ٱلْأَمْرُ وَهُمْ فِى غَفْلَةٍۢ وَهُمْ لَا يُؤْمِنُونَ ﴾

“hence, warn them of [the coming of] the Day of Regrets, when everything will have been decided-for as yet they are heedless, and they do not believe [in it].”

Please check ayah 19:40 for complete tafsir.