Exodus 7:15-17

Young's Literal Translation

¹⁵ go unto Pharaoh in the morning, lo, he is going out to the water, and thou hast stood to meet him by the edge of the River, and the rod which was turned to a serpent thou dost take in thy hand,

¹⁶ and thou hast said unto him: Jehovah, God of the Hebrews, hath sent me unto thee, saying, Send My people away, and they serve Me in the wilderness; and lo, thou hast not hearkened hitherto.

¹⁷ `Thus said Jehovah: By this thou knowest that I [am] Jehovah; lo, I am smiting with the rod which [is] in my hand, on the waters which [are] in the River, and they have been turned to blood,