John Calvin Reformed @genevareformer

22. Israel is my son, even my first-born. God thus refutes, by anticipation, the only pretext by which Pharaoh could justify his refusal to let the people go. For Jacob had spontaneously submitted himself and all his family to his government; he had then free power to retain the people, which, by the common law of nations, was subject to the dominion of Egypt.

Matthew Henry Presbyterian @wholebiblehenry

Here, I. Moses obtains leave of his father-in-law to return into Egypt, Exo 4:18. His father-in-law had been kind to him when he was a stranger, and therefore he would not be so uncivil as to leave his family, nor so unjust as to leave his service, without giving him notice.

Commenting on Exodus 4:18-23

John Gill Reformed Baptist @doctorgill

And thou shall say unto Pharaoh,.... When arrived in Egypt, and in his presence: thus saith the Lord; he was to declare to him that he came in his name, and by his orders, and, as an ambassador of his, required the dismission of the children of Israel out of Egypt: Israel is my son, even my firstborn; as dear to him as a man's...