Surah 20. Ta-Ha, Ayah 24

This seems to be a reference to Pharaoh’s greatest sin, namely, his claim to divine status (cf. 28:38 and 79:24 ).

Moses, having been spiritually prepared now gets his definite commission to go to Pharaoh and point out the error of his ways. So inordinate was Pharaoh's vanity that he had it in his mind to say: "I am your Lord Most High!" (lxxix. 24).