Quran 18:104 from Surah Al-Kahf on Divine Marvels.
ٱلَّذِينَ ضَلَّ سَعۡيُهُمۡ فِي ٱلۡحَيَوٰةِ ٱلدُّنۡيَا وَهُمۡ يَحۡسَبُونَ أَنَّهُمۡ يُحۡسِنُونَ صُنۡعًا
English translation: Those is lost their effort in the life (of) the world while they think that they (were) acquiring good (in) work
Transliteration: alladhina dalla sa'yuhum fi al-hayati al-dun'ya wahum yahsabuna annahum yuh'sinuna sun'an