وَأَنذِرْهُمْ يَوْمَ ٱلْحَسْرَةِ إِذْ قُضِىَ ٱلْأَمْرُ وَهُمْ فِى غَفْلَةٍ وَهُمْ لَا يُؤْمِنُونَ 
  Waan th irhum yawma al h asrati i th  qu d iya alamru wahum fee ghaflatin wahum l a  yuminoon a      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].
   - Mohammad Asad
     
O Muhammad, forewarn them about the Day of intense regret when    this matter will be decided, even though at present they are    paying no heed and do not believe.
   - Muhammad Farooq-i-Azam Malik
   And warn them 'O Prophet' of the Day of Regret, when all matters will be settled, while they are 'engrossed' in heedlessness and disbelief.
   - Mustafa Khattab
     
And warn them of the Day of anguish when the case hath been    decided. Now they are in a state of carelessness, and they    believe not.
   - Marmaduke Pickthall
   But warn them of the Day of Distress when the matter will be    determined: for (behold) they are negligent and they do not    believe! 2491
   - Abdullah Yusuf Ali