Qur'an 18:104

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."”

Al-Kahf 18:104 · Saheeh International