Exodus 14:4-5

4And I will harden1 Pharaoh’s heart so that he will pursue them. But I will gain honor by means of Pharaoh and all his army, and the Egyptians will know that I am the LORD.”

So this is what the Israelites did.

5When the king of Egypt was told that the people had fled, Pharaoh and his officials changed their minds about them and said, “What have we done? We have released Israel from serving us.”