Ibn Ezra on Exodus 4:9/אבן עזרא על שמות ד׳:ט׳

1AND IT SHALL COME TO PASS. If there shall still be a few Israelites that will not believe the last sign, then you will show them the third sign and they shall believe. Indeed, it is written, and (Moses) did the signs in the sight of the people (v. 30). This third sign, namely, and the water…shall become blood upon the dry land was part of the first of the ten plagues which were destined to come.