Moshe said to Paroh "Gloat over me! For when should I entreat on behalf of you, your servants, and your people, to cut off the frogs from you and your houses, that they shall remain only in the river?"
The Ohr Hachaim asks what is the explanation of this gloating that Par’oh can do. Does it mean he can gloat by demanding an immediate removal of the plague? Does that mean that Par’oh declined the offer and did not gloat over Moshe? If so, why did he say in the next possuk כִדְבָרְךָ – As you say, as though Par’oh had accepted his offer to gloat over him. Par’oh declined the offer and pushed off the end of the plague.
Additionally, what did Moshe mean with his words לְמָתַי אַעְתִיר – For when should I retreat, why did he not just say ‘when do you want the frogs to disappear’?
The Ohr Hachaim explains that Moshe wished to show him how much Hashem loves His people. Par’oh could learn that Hashem would never abandon His nation, and Par’oh would never win against them.
When a slave requests something from his master, it would be unethical for him to tell him when and how to give him the gift. He accepts that which he is offered and given. But when Moshe Rabbeinu requests something from his Loving Father, he can even put a time and date to it, because Hashem does everything that is good for His nation. This was Moshe Rabbeinu’s intention by his offer to stop the plague whenever Par’oh asked.
Par’oh’s answer was that he wanted it stopped tomorrow. This makes no sense. As evil as Par’oh was, he wouldn’t do something to make himself suffer. Why would he want another day of the plague?
The Ohr Hachaim explains that Par’oh saw how Moshe made himself available exactly as Par’oh would want, he suspected him of having some plan up his sleeve. He must have known that Hashem’s power was about to reach its limits, and the plague was about to end, and that is why he was willing to allow him to decide when the plague would come to an end. Moshe would have no reason to think that Par’oh would push off the end of the plague.
Par’oh did a trick on Moshe, demanding that he daven on that day, and the plague end the next day. No idol could pull off this trick.
Moshe’s answer to him was כִדְבָרְךָ – as you say. Moshe told him that this would teach him לְמַעַן תֵּדַע כִּי אֵין כַּה' אֱלֹוקינוּ – that there is none like Hashem. Hashem could do that and Hashem listens to the tefillos of His children. Just as they pray, with all conditions.
As soon as Moshe left Par’oh וַיֵּצֵּא מֹשֶׁה וְאַהֲרֹן מֵּעִם פַרְעֹה, and Moshe cried out to Hashem regarding the frogs that He had set on Par’oh. Par’oh would not trust that they did not wait until the next day to daven, so they davened immediately as Par’oh could see them.
They davened עַל דְּבַר הַצְּפַרְּ דְּעִים – regarding the frogs. Not just that they should disappear, but that they should disappear as Par’oh demanded, on the next day.
