﴿ 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].”

And warn them threaten O Muhammad (s) the disbelievers of Mecca of the Day of Regret namely the Day of Resurrection on which the sinner will regret not having been virtuous in the life of this world when the matter will be decided for them thereupon that they be chastised while they in this world are yet heedless of it and do not believe in it the Day of Resurrection.