But the Lord said to Moses, “Now you shall see what I will do to Pharaoh; for with a strong hand he will send them out, and with a strong hand he will drive them out of his land.”
And the Lord said to Moses, “When you go back to Egypt, see that you do before Pharaoh all the miracles that I have put in your power. But I will harden his heart, so that he will not let the people go.
Moses and Aaron did all these wonders before Pharaoh, and the Lord hardened Pharaoh’s heart, and he did not let the people of Israel go out of his land.
For when Pharaoh stubbornly refused to let us go, the Lord killed all the firstborn in the land of Egypt, both the firstborn of man and the firstborn of animals. Therefore I sacrifice to the Lord all the males that first open the womb, but all the firstborn of my sons I redeem.’