The translator should not try to reconcile this verse with verse 21. There is no indication where the magicians of Egypt found water that was not already blood. Magicians included both “wise men” and “sorcerers,” according to 7.11. Did the same probably means they “performed the same trick” (Translator’s Old Testament), but there is no clear indication that they used their rods. The point is that they also changed water into blood by their secret arts, “with their secret powers,” or “by means of their magic” (Good News Translation). In a number of languages it will be helpful to express this first sentence as “But the Egyptian magicians used their magic [or, secret powers] to do the same thing.”

So Pharaoh’s heart remained hardened is literally “and the heart of Pharaoh was hard.” The idea of remained is only an interpretation. The word for “hard” in this verse is the word meaning “strong,” as in 4.21. The idiom “hard heart” means “stubborn,” of course. But the king’s stubbornness was a result of what the magicians did. Therefore some translations suggest that Pharaoh’s heart may have softened a bit when he saw what Aaron (Moses?) had done. This is also possible. As explained in the comment at 7.13, this is one of the places where the idiom is “theologically neutral.”

And he would not listen to them means that he “rejected the demands” (Translator’s Old Testament) of Moses and Aaron. As the LORD had said again refers back to 7.4, where this had been “foretold” (New English Bible, New Jerusalem Bible, Translator’s Old Testament).

The second part of this verse, beginning with so Pharaoh’s heart, is identical with verse 13. Again, in a number of languages it will be helpful to put the clause as the LORD had said at the beginning of 7.22b and say “The king did just as the LORD had said he would do. He stubbornly refused to listen to Moses and Aaron.”

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .