Quran 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."

Translation · Saheeh International