Exodus 3:18-20

And they will listen to your voice, and you and the elders of Israel shall go to the king of Egypt and say to him, ‘The LORD, the God of the Hebrews, has met with us; and now, please let us go a three days’ journey into the wilderness, that we may sacrifice to the LORD our God.’ But I know that the king of Egypt will not let you go unless compelled by a mighty hand. So I will stretch out my hand and strike Egypt with all the wonders that I will do in it; after that he will let you go.