فَلَعَلَّكَ بَاخِعٌ نَّفْسَكَ عَلَى آثَارِهِمْ إِن لَّمْ يُؤْمِنُوا بِهَذَا الْحَدِيثِ أَسَفًا
[18:6]
Then maybe you will kill yourself with grief, sorrowing after them, if they do not believe in this announcement.
Thou wouldst only, perchance, fret thyself to death, following after them, in grief, if they believe not in this Message.
Yet it may be, if they believe not in this statement, that thou (Muhammad) wilt torment thy soul with grief over their footsteps.