18:6
فَلَعَلَّكَ بَـٰخِعٌ نَّفْسَكَ عَلَىٰٓ ءَاثَـٰرِهِمْ إِن لَّمْ يُؤْمِنُوا۟ بِهَـٰذَا ٱلْحَدِيثِ أَسَفًا
Then perhaps you would kill yourself through grief over them, [O Muhammad], if they do not believe in this message, [and] out of sorrow.
The Cave
فَلَعَلَّكَ بَـٰخِعٌ نَّفْسَكَ عَلَىٰٓ ءَاثَـٰرِهِمْ إِن لَّمْ يُؤْمِنُوا۟ بِهَـٰذَا ٱلْحَدِيثِ أَسَفًا
Then perhaps you would kill yourself through grief over them, [O Muhammad], if they do not believe in this message, [and] out of sorrow.
Nearby ayahs help place verse 18:6 in sequence and meaning.
وَيُنذِرَ ٱلَّذِينَ قَالُوا۟ ٱتَّخَذَ ٱللَّهُ وَلَدًا
And to warn those who say, "Allah has taken a son."
مَّا لَهُم بِهِۦ مِنْ عِلْمٍ وَلَا لِـَٔابَآئِهِمْ ۚ كَبُرَتْ كَلِمَةً تَخْرُجُ مِنْ أَفْوَٰهِهِمْ ۚ إِن يَقُولُونَ إِلَّا كَذِبًا
They have no knowledge of it, nor had their fathers. Grave is the word that comes out of their mouths; they speak not except a lie.
إِنَّا جَعَلْنَا مَا عَلَى ٱلْأَرْضِ زِينَةً لَّهَا لِنَبْلُوَهُمْ أَيُّهُمْ أَحْسَنُ عَمَلًا
Indeed, We have made that which is on the earth adornment for it that We may test them [as to] which of them is best in deed.
وَإِنَّا لَجَـٰعِلُونَ مَا عَلَيْهَا صَعِيدًا جُرُزًا
And indeed, We will make that which is upon it [into] a barren ground.