We continue with chapter 1 of Maseches Shevuos, mishnah 3. This mishnah continues to deal with the laws of awareness of tumah - with someone who ate kodashim or entered the Beis HaMikdash while he was tamei.
In the previous mishnah we learned two situations: one who knew that he was tamei, forgot his tumah, entered the Mikdash or ate kodashim, and afterward remembered what he had done - he brings a korban oleh v'yored. But if he had awareness at the beginning and forgot, and at the end he still had not become aware of it - the goat performed inside and Yom Kippur, the two of them together, suspend and protect him until he becomes aware that he was tamei, and then he brings an oleh v'yored. For a korban oleh v'yored is brought only when there is awareness at the beginning and awareness at the end.
The case in our mishnah:
The mishnah before us deals with one in whom "ein bah yediah batechilah aval yesh bah yediah basof" - he had no original awareness that he was tamei, but he became aware of it afterward, and during that period in which he was tamei and did not realize it, he ate kodashim or entered the Beis HaMikdash.
The Gemara explains that this scenario, in which a person has no awareness at all, refers to someone who never learned Torah beforehand - such as a child taken captive among the gentiles, who was not even aware of the very concept of tumah. And nevertheless, "yesh bah yediah basof" - in the end he became aware that tumah had been upon him.
The goat performed outside:
In such a case, says the mishnah, "sa'ir hana'aseh bachutz v'Yom HaKippurim mechaper" - the goat brought as a korban chatas is performed outside, not in the innermost chamber in the Kodesh HaKodashim, but on the outer mizbeach, and it is one of the musaf offerings brought on Yom Kippur. It is not part of the korbanos mentioned in Parashas Acharei Mos, but rather one of the korbanos mentioned in Parashas Pinchas together with the rest of the musafim.
The source of the law:
What is the source for this? The verse says, in mentioning the goat brought on Yom Kippur as a musaf: "milvad chatas hakippurim" - aside from the chatas brought in the Kodesh HaKodashim in the passage of Yom Kippur. From here we learn "mah shezeh mechaper, zeh mechaper" - that both of them atone for the same type of thing, and in the words of the mishnah: "mah hapenim eino mechaper ela al davar sheyesh bo yediah" - just as the inner one atones only for something in which there is awareness, so too the outer one atones only for something in which there is awareness.
The goat performed inside: As we learned in the previous mishnah, the goat performed in the Kodesh HaKodashim atones for something in which there is awareness. Clearly this does not mean awareness at the beginning and at the end together, for if so the korban would be an oleh v'yored; rather there is only one awareness - the original awareness at the beginning, while at the end he did not become aware.
The goat performed outside: It too, brought as a musaf, atones for something in which there is awareness - except that here it is awareness at the end, as stated at the opening of our mishnah: there is no awareness at the beginning but there is awareness at the end.
It emerges that the point of similarity between the two is that in both there is awareness: in one, awareness at the beginning, and in the other, awareness at the end alone. Joining them together in a hekesh teaches this similarity between them, and from here we learn that the korban brought outside on Yom Kippur atones for one who did not know at the beginning that he was tamei, and became aware of it afterward.
In summary: In this mishnah we learned the law of one who has no awareness at the beginning but does have awareness at the end - such as a child taken captive - who ate kodashim or entered the Mikdash while tamei: the goat performed outside and Yom Kippur atone for him. The source of the law is the verse "milvad chatas hakippurim", from which the inner goat and the outer goat are compared to one another, teaching us that just as the inner one atones only for something in which there is awareness, so too the outer one.