[They are] those whose effort is lost in worldly life, while they think that they are doing well in work."
The Saheeh International Quran Translation
ٱلَّذِينَ ضَلَّ سَعْيُهُمْ فِى ٱلْحَيَوٰةِ ٱلدُّنْيَا وَهُمْ يَحْسَبُونَ أَنَّهُمْ يُحْسِنُونَ صُنْعًا[They are] those whose effort is lost in worldly life, while they think that they are doing well in work."