Exodus 11:4-9

So Moses said to the king, “This is what the LORD says: ‘About midnight tonight I will go through all Egypt. Every firstborn son in the land of Egypt will die—from the firstborn son of the king, who sits on his throne, to the firstborn of the slave girl grinding grain. Also the firstborn farm animals will die. There will be loud outcries everywhere in Egypt, worse than any time before or after this. But not even a dog will bark at the Israelites or their animals.’ Then you will know that the LORD treats Israel differently from Egypt. All your officers will come to me. They will bow facedown to the ground before me and say, ‘Leave and take all your people with you.’ After that, I will leave.” Then Moses very angrily left the king. The LORD had told Moses, “The king will not listen to you and Aaron so that I may do many miracles in the land of Egypt.”