And it shall come to pass, if they will not believe also these two signs, neither hearken unto thy voice, that thou shalt take of the water of the river, and pour it upon the dry land: and the water which thou takest out of the river shall become blood upon the dry land.
If they don't believe in the two signs and listen to your voice, you should take water from the river and pour it on the dry land. The water you take will turn into blood on the dry land.