וַיַּֽעֲשׂוּ־כֵן֩ מֹשֶׁ֨ה וְאַהֲרֹ֜ן כַּאֲשֶׁ֣ר ׀ צִוָּ֣ה יְהוָ֗ה וַיָּ֤רֶם בַּמַּטֶּה֙ וַיַּ֤ךְ אֶת־הַמַּ֙יִם֙ אֲשֶׁ֣ר בַּיְאֹ֔ר לְעֵינֵ֣י פַרְעֹ֔ה וּלְעֵינֵ֖י עֲבָדָ֑יו וַיֵּהָֽפְכ֛וּ כָּל־הַמַּ֥יִם אֲשֶׁר־בַּיְאֹ֖ר לְדָֽם׃
모세와 아론이 여호와의 명하신 대로 행하여 바로와 그 신하의 목전에서 지팡이를 들어 하수를 치니 그 물이 다 피로 변하고
Chizkuni
ויהפכו כל המים אשר ביאור לדם, “all the water in the river had been turned into blood.” The river had been turned into blood only temporarily, and the fish died immediately on account of being unable to survive in a river of blood. As soon as all the fish had died, the river reverted to being water. As to the Torah having written that “the Egyptians could not drink water from the river,” this was not on account of the blood, for we do not find that they even tried to reverse the plague, but that was, as the Torah writes, because the stench of the water on account of all the dead fish. The proof of this is that the Torah writes: ויעשו כן כל חרטומי מצרים, “all of the sorcerers of Egypt performed a similar miracle;” if the waters had not first been restored, how could they have demonstrated their sorcery? Some commentators claim that the plague lasted for slightly over a week, a quarter of a month, for all waters visible to the people during that period. During that period, the sorcerers busied themselves with subterranean water. Their proof is that the Torah writes that “the Egyptians dug all around the river to find water as they could not drink the water from the river.” (verse 24). The subterranean waters had not been turned into blood.
Ramban
AND HE LIFTED UP THE ROD, AND SMOTE THE WATERS THAT WERE IN THE RIVER IN THE SIGHT OF PHARAOH. That is to say, Aaron lifted up the rod and stretched out his hand over the land of Egypt in all directions,125Ramban’s intent is to state that the lifting up of the rod, mentioned here in Verse 20, is identical with “stretch out thy hand,” mentioned in G-d’s command in Verse 19. Ibn Ezra, as stated further in the text, differs with this opinion. and afterwards he smote the waters that were in the river, in the sight of Pharaoh. In Pharaoh’s sight, all the waters that were in the river turned to blood, and the blood was furthermore throughout all the land of Egypt.126Verse 21. Ramban thus explains that the waters that were in the river turned to blood by reason of the smiting of the rod, while the waters in all other places turned into blood by reason of Aaron’s stretching forth his hand in all directions (Bachya). And Rabbi Abraham ibn Ezra said that Scripture mentioned the smiting of the river but found it unnecessary to mention the stretching out of the hand [in all directions] over the entire land of Egypt.127Thus according to Ibn Ezra, Scripture merely shortened its account here and did not mention the stretching out of Aaron’s hand, but not, as Ramban has it, that the stretching out of the hand is already included in the act of the smiting of the waters of the river.
Rashbam
לעיני פרעה, this was a big boost for Moses’ stature, that Aaron, merely his messenger, was able to accomplish this and use his staff on a regular basis.