And Moses and Aaron did all these wonders before Pharaoh: and the LORD hardened Pharaoh's heart, and he did not let the children of Israel go out of his land.
and it came to pass, when Pharaoh would hardly let us go, that the LORD slew all the firstborn in the land of Egypt, both the firstborn of man, and the firstborn of beast: therefore I sacrifice to the LORD all that openeth the womb, being males; but all the firstborn of my sons I redeem.
And the LORD said unto Moses, When thou goest back into Egypt, see that thou do before Pharaoh all the wonders which I have put in thine hand: but I will harden his heart, and he will not let the people go.
And the LORD said unto Moses, Now shalt thou see what I will do to Pharaoh: for by a strong hand shall he let them go, and by a strong hand shall he drive them out of his land.
And Pharaoh sent, and, behold, there was not so much as one of the cattle of the Israelites dead. But the heart of Pharaoh was stubborn, and he did not let the people go.