Exodus 4:8-10

Amplified Bible

⁸ “If they will not believe you or pay attention to the evidence of the first sign, they may believe the evidence of the second sign. ⁹ But if they will not believe these two signs or pay attention to what you say, you are to take some water from the Nile and pour it on the dry ground; and the water which you take out of the river will turn into blood on the dry ground.”

¹⁰ Then Moses said to the Lord, “Please, Lord, I am not a man of words (eloquent, fluent), neither before nor since You have spoken to Your servant; for I am ^[a]slow of speech and tongue.”