Sura 18 Al-Kahf (The Cave), aya 104

1. الَّذِينَ ضَلَّ سَعْيُهُمْ فِي الْحَيَاةِ الدُّنْيَا 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."

   18:104

Tafsiri: Saheeh International