What did God say He would do to Goshen during the plague of flies?
During the plague of flies, God said He would sever or separate the land of Goshen, where His people dwell, so that no swarms of flies would be there. This would show that He is the Lord in the midst of the earth.
Les explains that in Exodus 8, the first three plagues came upon Israel as well as Egypt, but at the plague of flies God made a difference. He said He would sever or separate the land of Goshen where His people dwell, so that no swarms of flies would be there. The purpose was that Pharaoh might know that the Lord is in the midst of the earth. Les ties this to the biblical principle of separation, seen earlier with Abraham, that God's people must be separated from the world around them before God can work.
And I will sever in that day the land of Goshen, in which my people dwell, that no swarms of flies shall be there; to the end thou mayest know that I am the LORD in the midst of the earth.