But when translates the conjunction waw. This introduces a relative clause that prepares the reader for the changed attitude of the Pharaoh, which is then described. Pharaoh saw may be understood literally, in that he “saw that the frogs were dead”; it may also be understood figuratively, in that he realized that the plague had been stopped. There was a respite means that “relief had been granted” (Jerusalem Bible). Other ways to express this are “When the king realized that things were back to normal” or “… that the frogs were no longer bothering him.” Contemporary English Version has “… things were now better.”

He hardened his heart means that the Pharaoh hardened his own heart. Good News Translation‘s “he became stubborn again” does not bring this out clearly enough. This is the first of three references in Exodus that place the blame for his stubbornness on the king himself. The same expression, using the same verb, is found in 8.32 and 9.34. The basic meaning of the verb is to make heavy. (But see the further comment at 4.21 and 7.13.)

And would not listen to them means that “he rejected the demands of Moses and Aaron” (Translator’s Old Testament) and refused to let the people go. As the LORD had said repeats the same phrase found in 7.13 and 8.19.

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 .