Va'eira. The Mitzrim were an Instrument of G'd's Will

Many Rishonim ask a question on this parsha, and that is, "Why were the Mitzrim punished, if they were merely instruments of Hashem's will, as expressed to Avraham at the Bris bein Habesarim?"  See Rambam 5 Hilchos Teshuva 1 et al. and 6 Hilchos Teshuva 11 and 12, and Raavad there. The Ramban in Lech Lecha also asks the question and says the second answer of the Raaved.

UPDATE: 
After posting this, and as discussed in the comments, I realized that it is incomplete without immediately mentioning two elements:  The Rishonim that say that the petur of Kaasher zamam velo kaasher assa is based on the evidence that what happened fulfilled Hashem's will; and the Ohr Hachayim's discussion of Yosef's statement to his brothers that "Elokim chashava letova."  Please bear these in mind while reading the rest of this.


I don’t understand what the Rambam is asking. First of all, why doesn’t he simply say like Reb Akiva that “Hakol tzafui vehareshu nesuna,” that all is foreseen but man still has free will?  This clearly means that Hashem foresees what will happen, but does not influence mankind's choices.  See Reb Meir Simcha in his pirush on the Rambam here where he has a special Ma’aracha called Hakol Tzafui, toward the end. Second of all, why is the Rambam asking davkeh because of the nevu’ah? Why isn’t it a general question of yedia and bechira? Elah mai, that it is a question specifically because they would have a teretz to excuse them from an onesh because they can say that Hashem had said this would happen. What kind of teretz is that?  Did they hold they had a din of Shor Ha'Itztadin, like the Mishna in Bava Kamma 39a, and like Rav on 40b, that not only is it not chayav missah, but is even kasher as a korban?


I think the pshat is that since this event was clearly retzon Hashem, then anyone who does it is doing a ma'aseh mitzva--albeit a mitzva shelo lishmah. And it is not shayich to be ma’anish a person for doing a mitzva even if his cheshbon was to do an aveira. For example, if a person is chayav an onesh misa from Beis Din, and he runs away and someone, who knows nothing of the court decision, kills him out of hatred in cold blood, that person certainly is not ne’enash; partly because the other is a gavra ketilla, but logically also because he is getting what he deserves.  Even though this is a good pshat, it sure isn’t what the Rambam has in mind.

The Lekach Tov here brings that this is why the first sign to Moshe was the nachash-it was a symbol that Hashem intended that the Mitzrim be like a rod to chastize the Bnei Yisroel, but the Mitzrim had changed from a rod to a snake, and hurt the Bnei Yisroel more than they deserved.

And the Gaon also speaks about this in Bo, Shemos 11:2 where it says “ve’yishalu...klei chesef....” He says: 1. That the main geula was by the Yam, because it was only there that the Mitzrim could be punished for having drowned the children. 2. That even at the Bris Bein Habsorim Hashem told Avrahom “ve'gam es hagoi asher ya’avodu dan Anochi,” and that this meant “if they do more that Hashem was gozer on the Jews. 3. That Yisro, when he said regarding Krias Yam Suf, “ki badavor asher zadu aleihem,” he meant that the mitzrim were more vicious than Hashem had decreed proper for the Jews because of “ze'don libam.”

And, when learning Makkos, I brought up the Ramban mentioned below in the parsha of zomemim on the idea of ‘velo ka’asher asa’, that this is because the fact that beis din punished him shows that he deserved it. I realized that this is the same idea— if the defendant deserved it, then even though the zomemim were resha’im who were unjustly accusing him of something he did not do, because they wanted to hurt him, they are not punished. And the same idea is true by a man that killed beshogeg— the mishnah in Avos that says that what happened was Hashem’s will. Then you have to apply the machlokes and the Ohr Hachayim about whether the act of a rasha carries out or subverts Hashem’s will, because if every rasha’s act carries out Hashem’s will, then according to the Ramban you shouldn’t be able to punish him. This is similar to the idea the Chinuch says about the issur of Nekama: Mitzvah 241 in Parshas Kedoshim, Vayikra 19:18; “A man should know and take to heart that all that happens to him from good to bad is intended to happen to him from Hashem, and from the hand of man...nothing will happen except His will Borch Hu, and so if a person causes him suffering or pain, a man should know in his soul that his sins caused it and Hashem decreed it upon him, and he should not direct his thoughts to revenge from the person because he is not the reason for the bad, rather the sin was the cause.” Of course, the Chinuch agrees that in cases where restitution is allowed, one can pursue restitution. But the idea is that one cannot bear a grudge against a malefactor for the pain he inflicted. This is hard to reconcile with the Ramban, unless you differentiate between injury by the hand of a jew and of a non-jew. But it doesn’t say “lo sikom berei’echa,” does it? And anyway the theology shouldn’t depend on the actor.