Think about the history that Egypt has had with the people of the Lord, at least in Scripture. Keep in mind how we read that Abraham in Genesis goes to Egypt and lies about Sarah because he is afraid that the ruler of Egypt will take her as his wife and in the process kill him. Then we can move on to Moses and how he grows up as the ruler of Egypt, even as a Hebrew, but then is forced to flee. He comes back and leads the people out of Egypt to the destruction of so many Egyptians.
Think about the role that Egypt plays in Jesus’ life. We read an oracle that is against Egypt from vs.1-15 where we see that Egypt is not considered an ally, but rather a foe. But that changes then in vs. 16. Your read in vs. 21 that “the Lord will make himself known to the Egyptians.” I interpret that in two different ways. One is found in Matthew 2:14-15 where we read that Joseph took his family into Egypt and by doing so brings the Savior into Egypt. As a Moses type Jesus comes out of Egypt bringing all that is needed to save the people of Israel.
But there is another passage that I absolutely love in Acts which strikes me as the Gospel being proclaimed in Egypt as well. If you look at Acts 8 you see the Ethiopian eunuch who is reading the prophet Isaiah and asks Philip to interpret it for him. Why would he not have been reading either this chapter or the previous chapter where Ethiopia is discussed? It is thought that this eunuch once he is baptized is the one who then proclaims the Gospel from Egypt all the way down in Eastern Africa to a people who are receptive to Jesus as Savior.