Targum for Exodus 7:17

כֹּ֚ה אָמַ֣ר יְהוָ֔ה בְּזֹ֣את תֵּדַ֔ע כִּ֖י אֲנִ֣י יְהוָ֑ה הִנֵּ֨ה אָנֹכִ֜י מַכֶּ֣ה ׀ בַּמַּטֶּ֣ה אֲשֶׁר־בְּיָדִ֗י עַל־הַמַּ֛יִם אֲשֶׁ֥ר בַּיְאֹ֖ר וְנֶהֶפְכ֥וּ לְדָֽם׃

thus saith the LORD: In this thou shalt know that I am the LORD—behold, I will smite with the rod that is in my hand upon the waters which are in the river, and they shall be turned to blood.

Targum Jonathan on Exodus