שְׂעִיר־עִזִּ֥ים אֶחָ֖ד לְחַטָּֽאת׃
satu ekor kambing jantan sebagai korban penghapus dosa;
Rabbeinu Bahya
ויעשו כן חרטומי מצרים, “the sorcerers of Egypt did likewise.” Seeing that all the water had turned into blood, where did the sorcerers take water from? We must therefore assume that Moses and Aaron struck only the waters of the Nile. This is supported by the words “the waters in the river” in our verse. Most of the verses dealing with the subject do not describe Moses and Aaron as striking “all the waters in Egypt.” Even verse 18 speaks only of the inability of the Egyptians to drink water “from the river.” It follows that the sorcerers had ample sources of water to draw on in order to demonstrate their skill. If we adopt this line of reasoning, how do we understand the words in verse 19 that Moses and Aaron were commanded to stretch out their hands over “all the waters of Egypt, over their rivers, over their ponds over their canals and over all their gathering of waters and they shall become blood?” How do we account for the fact that apparently Moses and Aaron did not comply fully with G’d’s command and struck only the waters in the river (verse 20)? We may answer this apparent omission by Moses and Aaron by remembering that the Nile was the primary source of water in Egypt and that all the ponds and canals were in the nature of tributaries receiving their water supply from the Nile. This, of course, brings us back to the question of “where did the חרטומים take water from to demonstrate their tricks?”
The answer is that they started digging in the ground. They found some water which they proceeded to turn into what looked like blood. Moses’ decree applied only to waters which were already visible as such not to subterranean pools of water. Alternatively, seeing that the sorcerers had heard the warning announcing this forthcoming plague, they had hastened to some areas where the water had not yet turned into blood, had taken some water out of its natural habitat and had then proceeded to demonstrate their skill in turning such water which had been divorced from its source into blood. They claimed that they had done this by their own efforts, though in fact, these waters also turned into blood once Moses and Aaron decreed that the waters in the Nile and those supplied by the Nile should turn into blood. You will note that Moses’ deed is attributed by the Torah to having occurred while Pharaoh and his servants were watching, i.e. לעיני פרעה ועבדיו, whereas it is not mentioned anywhere that Pharaoh or his servants actually watched the water used by the sorcerers changing into blood (verse 22).
The answer is that they started digging in the ground. They found some water which they proceeded to turn into what looked like blood. Moses’ decree applied only to waters which were already visible as such not to subterranean pools of water. Alternatively, seeing that the sorcerers had heard the warning announcing this forthcoming plague, they had hastened to some areas where the water had not yet turned into blood, had taken some water out of its natural habitat and had then proceeded to demonstrate their skill in turning such water which had been divorced from its source into blood. They claimed that they had done this by their own efforts, though in fact, these waters also turned into blood once Moses and Aaron decreed that the waters in the Nile and those supplied by the Nile should turn into blood. You will note that Moses’ deed is attributed by the Torah to having occurred while Pharaoh and his servants were watching, i.e. לעיני פרעה ועבדיו, whereas it is not mentioned anywhere that Pharaoh or his servants actually watched the water used by the sorcerers changing into blood (verse 22).