Al-Kahf 104

ٱلَّذِينَ ضَلَّ سَعْيُهُمْ فِى ٱلْحَيَوٰةِ ٱلدُّنْيَا وَهُمْ يَحْسَبُونَ أَنَّهُمْ يُحْسِنُونَ صُنْعًا

alladhīna ḍalla saʿyuhum fī l-ḥayati l-dun'yā wahum yaḥsabūna annahum yuḥ'sinūna ṣun'ʿan

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