Quran 18:6 from Surah Al-Kahf on Divine Marvels.
فَلَعَلَّكَ بَٰخِعٞ نَّفۡسَكَ عَلَىٰٓ ءَاثَٰرِهِمۡ إِن لَّمۡ يُؤۡمِنُواْ بِهَٰذَا ٱلۡحَدِيثِ أَسَفًا
English translation: Then perhaps you would (be) the one who kills yourself over their footsteps if not they believe in this [the] narration (in) grief
Transliteration: fala'allaka bakhi'un nafsaka ala atharihim in lam yu'minu bihadha al-hadithi asafan