Exodus 7:15-16

Go to Pharaoh in the morning; when he goes out to the water, you will be waiting for him by the edge of the Nile, with the rod which was turned into a snake in your hand; And say to him, The Lord, the God of the Hebrews, has sent me to you, saying, Let my people go so that they may give me worship in the waste land; but up to now you have not given ear to his words.