Exodus 14:4-5

4And once again I will harden Pharaoh’s heart, and he will chase after you. I have planned this in order to display my glory through Pharaoh and his whole army. After this the Egyptians will know that I am the Lord!” So the Israelites camped there as they were told.

5When word reached the king of Egypt that the Israelites had fled, Pharaoh and his officials changed their minds. “What have we done, letting all those Israelite slaves get away?” they asked.