Qur'an 18:104 · Al-Kahf

ٱلَّذِينَ ضَلَّ سَعْيُهُمْ فِى ٱلْحَيَوٰةِ ٱلدُّنْيَا وَهُمْ يَحْسَبُونَ أَنَّهُمْ يُحْسِنُونَ صُنْعًا

(104) [They are] those whose effort is lost in worldly life, while they think that they are doing well in work."