Exodus 7:3-5 is one of the passages that describe God's purpose for the plagues. "But I will harden Pharaoh's heart, and though I multiply my miraculous signs and wonders in Egypt, he will not listen to you. Then I will lay my hand on Egypt and with mighty acts of judgment I will bring out my divisions, my people the Israelites. And the Egyptians will know that I am the LORD when I stretch out my hand against Egypt and bring the Israelites out of it."