Exodus 3:17-20

17And I have promised to bring you up out of your misery in Egypt into the land of the Canaanites, Hittites, Amorites, Perizzites, Hivites and Jebusites—a land flowing with milk and honey.’

18“The elders of Israel will listen to you. Then you and the elders are to go to the king of Egypt and say to him, ‘The Lord, the God of the Hebrews, has met with us. Let us take a three-day journey into the wilderness to offer sacrifices to the Lord our God.’

19But I know that the king of Egypt will not let you go unless a mighty hand compels him.

20So I will stretch out my hand and strike the Egyptians with all the wonders that I will perform among them. After that, he will let you go.