الَّذِينَ ضَلَّ سَعْيُهُمْ فِي الْحَيَاةِ الدُّنْيَاThose whose efforts have been wasted in this life,meaning, they did deeds that do not count, deeds that are not in accordance with the prescribed way that is acceptable to Allah.وَهُمْ يَحْسَبُونَ أَنَّهُمْ يُحْسِنُونَ صُنْعًاwhile they thought that they were acquiring good by their deeds.means, they thought that there was some basis for their deeds and that they were accepted and loved