Exodus 7:15-17

American Standard Version

¹⁵ Get thee unto Pharaoh in the morning; lo, he goeth out unto the water; and thou shalt stand by the river’s brink to meet him; and the rod which was turned to a serpent shalt thou take in thy hand. ¹⁶ And thou shalt say unto him, Jehovah, the God of the Hebrews, hath sent me unto thee, saying, Let my people go, that they may serve me in the wilderness: and, behold, hitherto thou hast not hearkened. ¹⁷ Thus saith Jehovah, In this thou shalt know that I am Jehovah: behold, I will smite with the rod that is in my hand upon the waters which are in the river, and they shall be turned to blood.