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."
The Cave
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."
Nearby ayahs help place verse 18:104 in sequence and meaning.
أَفَحَسِبَ ٱلَّذِينَ كَفَرُوٓا۟ أَن يَتَّخِذُوا۟ عِبَادِى مِن دُونِىٓ أَوْلِيَآءَ ۚ إِنَّآ أَعْتَدْنَا جَهَنَّمَ لِلْكَـٰفِرِينَ نُزُلًا
Then do those who disbelieve think that they can take My servants instead of Me as allies? Indeed, We have prepared Hell for the disbelievers as a lodging.
قُلْ هَلْ نُنَبِّئُكُم بِٱلْأَخْسَرِينَ أَعْمَـٰلًا
Say, [O Muhammad], "Shall we [believers] inform you of the greatest losers as to [their] deeds?
أُو۟لَـٰٓئِكَ ٱلَّذِينَ كَفَرُوا۟ بِـَٔايَـٰتِ رَبِّهِمْ وَلِقَآئِهِۦ فَحَبِطَتْ أَعْمَـٰلُهُمْ فَلَا نُقِيمُ لَهُمْ يَوْمَ ٱلْقِيَـٰمَةِ وَزْنًا
Those are the ones who disbelieve in the verses of their Lord and in [their] meeting Him, so their deeds have become worthless; and We will not assign to them on the Day of Resurrection any importance.
ذَٰلِكَ جَزَآؤُهُمْ جَهَنَّمُ بِمَا كَفَرُوا۟ وَٱتَّخَذُوٓا۟ ءَايَـٰتِى وَرُسُلِى هُزُوًا
That is their recompense - Hell - for what they denied and [because] they took My signs and My messengers in ridicule.