Quran 6:15 from Surah Al-An'aam on Divine Marvels.
قُلۡ إِنِّيٓ أَخَافُ إِنۡ عَصَيۡتُ رَبِّي عَذَابَ يَوۡمٍ عَظِيمٖ
English translation: Say Indeed, I [I] fear if I disobeyed my Lord punishment (of) a Day Mighty
Transliteration: qul inni akhafu in asaytu rabbi adhaba yawmin azimin