“And G-d said to Aharon, ‘you and your sons and the House of Your Father will bear the sin of the Sanctuary, and you and your sons will bear the sin of your Priesthood” (Bamidbar 18:1). Rashi tells us that even though the Torah says that G-d said this to Aharon (without Moshe being mentioned), this communication was really said to Moshe, who was told to communicate it to Aharon. The Sifre (117) is usually cited as Rashi’s source, but that Midrash is explaining a different verse (8:8), leading many commentaries to discuss why Rashi took a concept that the Midrash taught on a later verse and applied it to this verse instead. However, there are other Midrashim (e.g. Sifre Zuta) which say that G-d communicated with Aharon through Moshe (and not directly with Aharon) regarding this verse, and they could be Rashi’s source. Nevertheless, it is still curious that the Sifre only teaches this on the later verse, while Rashi chose to teach it on this earlier verse.
Even more curious is that Rashi (Vayikra 1:1) quotes Toras Kohanim (Dibura d’N’dava 1:2:1), which says that there are 13 places in the Torah where the verbiage excludes Aharon from having direct communication with G-d, and since there are 11 times where there is a “dibur” (a more direct form of communication than “amirah”) to both Moshe and Aharon, and two where the “dibur” is to only Aharon (and the 13 “exclusions” are said to exclude “dibur”), this indicates that when the communication is described as an “amirah” (rather than a “dibur”) it could have been directly with Aharon. Since the communication described in 8:1 was an “amirah,” if only those described as a “dibur” were excluded, how can Rashi tell us that this communication was also excluded, with G-d not speaking to Aharon directly but telling Moshe to relay the communication to him?
As far as the Sifre is concerned, since it also references the 13 exclusions (at the end of Parashas Naso), only mentioning Aharon being excluded from direct communication with G-d on 8:8, which is a “dibur,” and not on 8:1, which is an “amirah,” makes sense. And since Rashi had already told us that for the 13 “dib’ros” where Aharon is mentioned the communication was not with Aharon directly, but through Moshe, there is no need for Rashi to say it again on 8:8. But how can Rashi apply this to the “amirah” of 8:1 as well?
[Interestingly, when there is a “dibur” to both Moshe and Aharon telling them to “separate from this congregation” so that G-d can “destroy them” (16:20-21), both Moshe and Aharon “fell on their faces and said, ‘Mighty One, G-d of the spirits of all flesh, one man sins and with the entire congregation You get angry?” If the “dibur” was only to Moshe, who then told it to Aharon, yet they both “fell on their faces,” Moshe must have waited to tell Aharon what G-d said before reacting to it. Even though G-d was already communicating with him, and “falling on his face” to beseech G-d not to destroy them would seem much smoother as a continuation of the same communication (which could have happened if the communication was to both Moshe and Aharon), since it was only with Moshe whom G-d was communicating, Moshe had to end that communication, go tell Aharon what G-d had just told him, and then restart his communication with G-d (while Aharon started his own communication with Him) in order to beg Him not to destroy the nation.
This may explain why Moshe thought that the “them” G-d meant to destroy was the entire nation, not just those who had sinned; even though he was told to “relay this communication to others” (“leimor”), Moshe thought G-d meant to relay it to Aharon, with the “them” who were to be destroyed referring to everyone else (i.e. the whole nation). What G-d really meant, though, is that he should tell the nation to separate from the sinners, with the “them” to be destroyed being the sinners. Since the words “and to Aharon” mean that Moshe should relay it to Aharon, not that Aharon was included in the communication, the word “leimor” must refer to someone other than Aharon, i.e. the nation. Moshe didn’t “see” this verse until he wrote it down afterwards, and may have misunderstood who was included in the “others” he was supposed to relay it to. Granted, it may be problematic to suggest that Moshe didn’t fully understand what G-d was telling him, but according to those commentators who understand the “back and forth” as Moshe misunderstanding who G-d meant to destroy (as opposed to G-d changing His mind because of Moshe and Aharon’s supplications), this could explain the mechanics of the misunderstanding.]
There are two ways to understand the difference between “amirah” (i.e. “vayomer”) and “dibur” (i.e. “vayidaber”), at least as far as whether Aharon was included or excluded. Because “amirah” is a less direct form of communication, it could include Aharon, as Aharon could (and, since he was also a prophet, did, at least sometimes) communicate directly with G-d (as opposed to “dibur,” which is reserved for Moshe). Or, because “amirah” could refer to a form of communication that is not direct at all, but a message relayed through someone else, such as when G-d told Rivka through Shem why she was having difficulty with her pregnancy (see Rashi on B’reishis 25:23) and when Yisro told Moshe through a third party that he and his daughter (Moshe’s wife) and their sons had arrived (see Rashi on Sh’mos 18:6), it could mean that G-d’s message for Aharon was relayed through someone else (i.e. Moshe).
Included in this communication (Bamidbar 8:1) were instructions for protecting the Sanctuary from those who didn’t belong, and by extension, for protecting those who don’t belong from being adversely affected by getting too close to the Sanctuary (which is what the nation had expressed concern about, and what these instructions were a response to). Since these instructions had the status of “Torah law,” they must have been taught through Moshe, with Moshe having communicated directly with G-d about it. Therefore, when the Torah says that G-d communicated this to Aharon, it must have been through Moshe. This was the point Rashi was making; even though “amirah” could refer to a direct communication between G-d and Aharon, in this case (at least) it wasn’t. Rather, Moshe was told to tell it to Aharon, who was in charge of protecting the Sanctuary.
When the Midrashim tell us that there are 13 “exclusions” to teach us that even though it says there was a “dibur” from G-d to Aharon it was really through Moshe (with Moshe telling it to Aharon), it doesn’t mean that only those communications that qualify as a “dibur” came through Moshe but those coming through an “amirah” were direct. Rather, only those that are described as being a “dibur,” which implies a more direct communication, need to be excluded so that we know it wasn’t a direct communication. Those communications described as an “amirah” don’t need to be excluded, as the fact that they are an “amirah” itself tells us that they aren’t necessarily a direct communication. There being 13 “exclusions” doesn’t automatically mean that all other communications were done directly, only that there were only 13 communications that needed exclusions. All the others could have been direct, or could have been through a third party (i.e. Moshe). This one, Rashi tells us, was through Moshe.