In the previous Mishnah, we learned that a Bechor (firstborn animal), whether it was blemished or unblemished, has to be slaughtered and eaten within the first year of its life. Here, we’ll talk about a Bechor that was born unblemished but later became blemished. The Mishnah says a Bechor was born unblemished and then developed a blemish. During the first year of its life, you’re allowed to keep it only for the rest of the 12 months from the day it was born before slaughtering it. The Kohen (priest) to whom the Bechor was given could wait 12 months before slaughtering the blemished Bechor. But if it develops a blemish after its first year, he’s allowed to keep it until 30 days from when that blemish develops.
We’re talking about a situation after the Bet HaMikdash (Temple) was destroyed, where an unblemished Bechor cannot be offered as a Korban (sacrifice). The Kohen has to keep the Bechor until it develops a blemish. At that point, it could be slaughtered and eaten. You have no way of offering it on a Mizbeach (altar); the Bet HaMikdash was destroyed. So you have to allow it to develop that blemish, and then you could eat it. During the time of the Bet HaMikdash, though, like the Mishnah told us previously, you have to eat the Bechor during the first year. In this situation, where we said it’s after the first year and then it develops a blemish, you only have 30 days to eat it. Even though the first year passed, you have another 30 days to keep the Bechor. If it develops a blemish even before that first year is complete, we give him 30 more days from the time the blemish develops. If he acquired the blemish 15 days before the end of the year, for example, he’s allowed to keep the Bechor for 15 days into the next year.