Moses and Aaron performed all these wonders before Pharaoh, but the Lord hardened Pharaoh’s heart, and he would not let the Israelites go out of his country.
When Pharaoh stubbornly refused to let us go, the Lord killed the firstborn of both people and animals in Egypt. This is why I sacrifice to the Lord the first male offspring of every womb and redeem each of my firstborn sons.’
The Lord said to Moses, “When you return to Egypt, see that you perform before Pharaoh all the wonders I have given you the power to do. But I will harden his heart so that he will not let the people go.
Then the Lord said to Moses, “Now you will see what I will do to Pharaoh: Because of my mighty hand he will let them go; because of my mighty hand he will drive them out of his country.”
Pharaoh investigated and found that not even one of the animals of the Israelites had died. Yet his heart was unyielding and he would not let the people go.