Surah Az-Zumar, Verse 13

قُلۡ إِنِّيٓ أَخَافُ إِنۡ عَصَيۡتُ رَبِّي عَذَابَ يَوۡمٍ عَظِيمٖ١٣

qul innī akhāfu in ʿaṣaytu rabbī ʿadhāba yawmin ʿaẓīmin

Say, "Indeed I fear, if I should disobey my Lord, the punishment of a tremendous Day."