Exodus 3:17-20

17and I have said, I will bring you up out of the affliction of Egypt, unto the land of the Canaanites, and the Hittites, and the Amorites, and the Perizzites, and the Hivites, and the Jebusites, unto a land flowing with milk and honey.

18And they shall hearken to thy voice. And thou shalt come, thou and the elders of Israel, unto the king of Egypt, and ye shall say unto him, Jehovah, the 1God of the Hebrews, hath met with us; and now, let us go, we pray thee, three days' journey into the wilderness, that we may sacrifice to Jehovah our 2God.

19But I know that the king of Egypt will not let you go, no, not by a powerful hand.

20And I will stretch out my hand and smite Egypt with all my wonders which I will do in the midst thereof; and after that he will let you go.