Exodus 4:8-9

8And it shall come to pass, if they will not believe thee, neither hearken to the voice of the first sign, that they will believe the voice of the other sign.

9And it shall come to pass, if they will not believe also those two signs, neither hearken unto thy voice, that thou shalt take of the water of the river, and pour [it] on the dry [land]; and the water that thou takest out of the river shall become blood upon the dry [land].