The Midrash writes that Moshe told Hashem that either he should heal Miriam or Moshe himself will do the job. Very strange – Moshe could do something without Hashem?
Ksav Sofer explains that Moshe was not sure what Miriam was guilty of – was it an issur bein adam laMakom or bein adam l’chaveiro? The Mishna tells us that Hashem does not give kapparah on a bein adam l’chaveiro unless and until the injured party is mochel. Moshe said to Hashem as follows: if Miriam is guilty of a bein adam laMakom, then Hashem, you give her mechilah and kapprah; if Miriam is guilty of a bein adam l’chaveiro and it’s all up to me, then I will do the job and pardon her.
It seems a little strange to me to categorize Miriam's wrongdoing did as a bein adam l’chaveiro. One of the ikkarim is that “lo kam navi k’Moshe.” Miriam is not considered guilty of violating ikkarei emunah, as it was only through Hashem’s response to this episode that this ikkar was revealed, but still, once Hashem did reveal that Moshe is in a class by himself, isn’t it also clear that Miriam’s wrongdoing should be considered a bein adam laMakom?
Rambam/Ramban disagree as to whether “rapo yirapeh” is a reshus for those who are not on the level of relying completely on Hashem to cure all ailments, or whether it is part of the necessary hishtadlus a person must make in order to live. Perhaps this was Moshe’s safeik – was he required to do something to cure Miriam, or was he supposed to leave it completely in Hashem’s hands? (Granted that since Miriam was suffering from tzara’as, it is hard to see what Moshe could have done.)
Chasam Sofer writes that part of what we are supposed to remember about this episode with Miriam is the fact that Bnei Yisrael waited for her for seven days before travelling. Chazal tell us that this was a reward / hakaras ha’tov for Miriam having waited a few minutes on the banks of the Nile to see what would happen to baby Moshe after the basket he was in was put in the river. Why is Miriam rewarded davka here for what she did so many years earlier?
Chasam Sofer explains that there are two ways to look at Miriam's actions. You could say that she waited for baby Moshe simply because she was her sister. The fact that normally a parent is more concerned for a son/daughter than a sibling, and we know that Yocheved and Amram did not stand and watch what happened, underscores the amount concern and love Miriam had for her little brother. For that, she deserves some reward. But there is another way to look at it. Why did Miriam alone spend the extra few minutes watching what would happen to baby Moshe? Because Miriam more than anyone else believed and had prophesized that this was not just her brother and not just any baby, but this was the moshian shel yisrael – a one of a kind. The reward for that type of emunah, says the Chasam Sofer, is not something that can be given in tangible goods of olam ha’zeh. A reward that great can only come in olam ha'ba.
Had it not been for this espisode of Miriam speaking against Moshe, then Hashem would have judged her l'kaf zechus and credited her not just with being a concerned sister, but for having emunah that her brother was the one who would redeem all of Klal Yisrael from galus and for helping to bring that dream to fruition. However, since Miriam failed to judge her brother l'kaf zechus -- since she spoke against Moshe without giving him the benefit of the doubt -- Hashem did not give her the benefit of the doubt. Waiting for Miriam for seven days in exchange for her waiting on the banks of the Nile and watching after Moshe is not a reward – it’s a punishment! Instead of her getting a super reward in olam ha’ba, she was now paid out in the paltry currency of olam ha’zeh for the lesser good of the two.
This, says the Chasam Sofer, is the mussar the Torah is telling us about lashon ha'ra. The way you look at others and judge them is exactly the way Hashem will look at you and judge you.
That sounds a little scary, so let me end on a more positive note. In one of R’ Ya’akov Shapira’s (R”Y of Merkaz haRav) sichot he deals with the same question but puts a positive spin on the answer. Hakaras ha’tov can only be fulfilled if a person is fully cognizant of the value of the gift he/she receives. For example, if someone were to give a child a toy made of solid gold, even if the child says thank you, to him/her it’s just a thank you for a shiny new toy. Later in life, when the child understands the true value of that “toy,” he/she hopefully will say thank you again with a different sense of appreciation. Miriam had undoubtedly been thanked for having been the one to look after baby Moshe. However, that thank you was like the thank you of the child who does not understand the full value of his/her gift. It is only after Hashem revealed at this moment that Moshe was in a class by himself, far above any other navi, that the true value of Miriam’s act could be appreciated as well. It was not just her brother that she saved and looked after, not just a future navi, not just the moshi’an shel yisrael, but someone the likes of whom would never exist again. In that light, the thank you and hakaras ha’tov of the past was not sufficient. Bnei Yisrael had to delay on her account and an expression of hakaras ha’tov that showed renewed appreciation for what she had done.