الكهف — Al-Kahf Ayat 104

اَلَّذِيْنَ ضَلَّ سَعْيُهُمْ فِى الْحَيٰوةِ الدُّنْيَا وَهُمْ يَحْسَبُوْنَ اَنَّهُمْ يُحْسِنُوْنَ صُنْعًا

Al-lażīna ḍalla sa‘yuhum fil-ḥayātid-dun-yā wa hum yaḥsabūna annahum yuḥsinūna ṣun‘ā(n).

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