وَقَالَ فِرْعَوْنُ ذَرُونِىٓ أَقْتُلْ مُوسَىٰ وَلْيَدْعُ رَبَّهُۥٓ إِنِّىٓ أَخَافُ أَن يُبَدِّلَ دِينَكُمْ أَوْ أَن يُظْهِرَ فِى ٱلْأَرْضِ ٱلْفَسَادَ
"Pharaoh said: 'Leave me to kill Moses; and let him call upon his Lord! For I fear that he will change your religion, or that he will bring corruption out into the land.'"
The construction of the sentence is odd, and the lexicographers dwell on it: the most powerful man in the country speaks as though asking someone's leave. I record this as an observation and transmit both readings: either there is an opinion around him that is holding him back, or this is for show — a sentence framed to display his resolve to those around him.
The second: the justification. Innī akhāfu an yubaddila dīnakum aw an yuẓhira fi'l-arḍi'l-fasād — "I fear."
I record this as my own reading, and its ground is the words themselves: the decision to kill is presented not with a claim to power but with a justification of protection. And the word in the justification is fasād — that is, the crime the other side is said to be about to commit is exactly the name of what is being committed here. The sūra does not interpret this; it transmits the sentence as it stands and leaves it there.