Exodus 4:8-10

Complete Jewish Bible

⁸ “If they won’t believe you or heed the evidence of the first sign, they will be convinced by the second. ⁹ But if they aren’t persuaded even by both these signs and still won’t listen to what you say, then take some water from the river, and pour it on the ground. The water you take from the river will turn into blood on the dry land.”

¹⁰ Moshe said to Adonai, “Oh, Adonai, I’m a terrible speaker. I always have been, and I’m no better now, even after you’ve spoken to your servant! My words come slowly, my tongue moves slowly.”