Surat Al-Kahf (The Cave) - الكهف

ٱلَّذِينَ ضَلَّ سَعْيُهُمْ فِى ٱلْحَيَوٰةِ ٱلدُّنْيَا وَهُمْ يَحْسَبُونَ أَنَّهُمْ يُحْسِنُونَ صُنْعًا ﴿١٠٤﴾

(These are) they whose labor is lost in this world's life and they think that they are well versed in skill of the work of hands.