And He said to Aharon: “Take for yourself a calf, a young male ox, as a sin-offering, and a ram for an Olah-offering, unblemished, and offer them before Hashem”.
Rashi seems to be bothered as to why Hashem would command Aharon to bring a young male calf as a sin-offering, when typically, it is an ox that a Kohen Gadol is commanded to bring as a sin-offering. Rashi goes on to give reason for it as follows, להודיע שכפר לו הקב"הקח לך עגל. על ידי עגל זה על מעשה העגל שעשה. - Take for yourself a calf. To inform Aharon that Hashem granted him atonement, through this calf, for the matter of the Golden Calf that he made. It would appear that Rashi is explaining that Hashem commanded Aharon to bring a calf so that it would atone for his sin of the Golden Calf.
The Sefer זרע ברך asks, why did Rashi need to explain this concept by saying that Aharon was commanded to bring a calf as a sin-offering להודיע שכפר לו הקב"ה על ידי עגל זה - in order to inform Him that Hashem granted him atonement, through this calf, for the matter of the Golden Calf that he made, when he could have simply stated; לכפר לו על ידי עגל זה – in order to grant him atonement, through this calf, for his sin of the Golden Calf?
The Gemara in Rosh Hashanah (כו ע"א) teaches us the following.
מפני מה אין כהן גדול נכנס בבגדי זהב לפני ולפנים לעבוד עבודה, לפי שאין קטיגור נעשה סניגור וכו', והא איכא ארון וכפורת וכרוב, חוטא בל יקריב קאמרינן – For what reason does a Kohen Gadol not enter the Holy of Holies in the golden garments to perform the service on Yom Kippur? Because an accuser cannot become a defender. Gold stands as an accuser of Israel, since it recalls the sin of the Golden Calf; therefore, it may not be worn by the Kohen Gadol when he seeks atonement for Israel through his service. The Gemara challenges this idea, that the reason why the Kohen Gadol does not wear gold in the Holy of Holies is because an ‘accuser’ may not become a ‘defender’, and asks the following; But there are the Ark, it’s cover and the Cheruvin which were all made of gold and stood in the Holy of Holies, and yet the Kohen Gadol entered there on Yom Kippur seeking atonement? The Gemara answers; We are saying only that a sinner should not bring close an item with which he has sinned. That is, while seeking atonement for Israel’s sins, the Kohen Gadol should not bring any item that recalls their sins into the Holy of Holies. The Ark, its cover and the Cheruvin, however, are fixed and permanent furnishings of the Holy of Holies.
The Jews can obviously never bring a calf as a sin-offering, for that would recall the sin of the Golden Calf, and ‘an accuser cannot become a defender’. It goes without saying that was Aharon to be guilty of the sin of the Golden Calf, he too would not have been able to bring a calf as a sin-offering. Consequently, when Hashem commanded Aharon “Take for yourself a calf, a young male ox, as a sin-offering”, we must say that Hashem was obviously not telling Aharon that this calf would atone for his sin of the Golden Calf, as ‘an accuser cannot become a defender’. Rather, this command to bring a calf as a sin-offering was informing Aharon that his sin of the Golden Calf had already been forgiven, and therefore he may henceforth bring a calf as a sin-offering.
We can now clearly understand and appreciate Rashi’s somewhat more lengthy explanation as to why Hashem commanded Aharon to bring a calf as a sin-offering. Rashi couldn’t simply say; ‘In order to grant him atonement, through this calf, for his sin of the Golden Calf’, which would suggest that the calf that was brought as a sin-offering was what would atone for the sin of the Golden calf, because that cannot be true, as we just explained. Rather what Rashi did say was; ‘In order to inform Him that Hashem granted him atonement, through this calf, for the matter of the Golden Calf that he made’. With which Rashi means to say as follows; Through Hashem commanding Aharon to bring a calf as a sin-offering, He was essentially informing Aharon that He has already granted him atonement for the sin of the Golden Calf.
(זרע שמשון פרשתנו אות א)