Exodus 11:5-10 NLT

5 All the firstborn sons will die in every family in Egypt, from the oldest son of Pharaoh, who sits on his throne, to the oldest son of his lowliest servant girl who grinds the flour. Even the firstborn of all the livestock will die.
6 Then a loud wail will rise throughout the land of Egypt, a wail like no one has heard before or will ever hear again.
7 But among the Israelites it will be so peaceful that not even a dog will bark. Then you will know that the makes a distinction between the Egyptians and the Israelites.
8 All the officials of Egypt will run to me and fall to the ground before me. ‘Please leave!’ they will beg. ‘Hurry! And take all your followers with you.’ Only then will I go!” Then, burning with anger, Moses left Pharaoh.
9 Now the had told Moses earlier, “Pharaoh will not listen to you, but then I will do even more mighty miracles in the land of Egypt.”
10 Moses and Aaron performed these miracles in Pharaoh’s presence, but the hardened Pharaoh’s heart, and he wouldn’t let the Israelites leave the country.