Комментарий к Киним 2:4

קן סתומה – he did not explain which was [designated/specified] for a sin-offering and which was [designated/specified] for a burnt-offering.

An unassigned pair and an assigned pair: if one bird from the unassigned [pair] flew to the assigned [pair], then a pair must be taken for the second [bird]. There are two pairs in the situations described in this mishnah. In one pair the two birds have been assigned which one will be a hatat and which one will be an olah. The birds of the other pair have not been assigned. One bird from the unassigned pair flies over to the assigned pair. The three birds are now mixed up such that we can't tell which one of the assigned pair was a hatat and which was an olah. These three birds cannot be sacrificed and must be left to die. The owner can then take a second bird for the one bird left in the unassigned pair. This is the case of one bird from an unassigned pair that flies into a group of birds that must be left to die (see mishnah one). As we learned, in such a case he may take another bird for the bird left in the original pair.

וקן מפורשת – that it is known that this one was [designated/specified] for a sin-offering and that one was [designated] for a burnt-offering. But here, we are speaking when the two pigeons were combined together after they were designated/specified, and now it is not known which is for a sin-offering and which is for a burnt offering, and this is shown in the concluding clause [of the Mishnah] that teaches: “or [if] at first one which had been designated flew off to the first undesignated pair, all of them are left to die, but if the individual pigeons that had been designated/specified did not became mixed with each other, why should they be [all] left to die, but if the burnt-offering flew off, the remaining [bird] for the sin-offering should be offered up, and similarly, the unspecified/undesignated couple of sacrificial birds , should be offered up as one burnt-offering because of the burnt-offering that became mixed up with it. But we are speaking of when individual pigeons that were designated became mixed up one with another, but if one individual pigeon from the pair of sacrificial birds had not been designated/specified had been combined with that which was designated, he (i.e., the Kohen) should take one pair for second [bird] and designate one for a sin-offering and one for a burnt-offering, and the third that had been combined/mixed up together, all of them should be left to die. If one from the three that had been mixed up/combined returned and became combined with the individual [bird] remaining from the undesignated/specified group, or at the outset of flying off, combined one from the designated [pair] to that which was not designated/specified, which is the first as we stat, meaning to say, that at the outset of flying off, one went and combined with an undesignated pair, all of them should be left to die, for since the individual pigeons which had been designated had combined together, they are no longer offered up, and when one of them flee off in another place, that is, one from the ones left to die that flew off among those that were to be offered up, all of them should be left to die.

If one bird flew back, or if in the first place a bird from the assigned pair flew [to the other pair], then all must be left to die. If one of the three birds left to die flew back to the other pair, then all of the birds must be left to die, for in neither of them do we know which is the hatat and which is the olah. The same is true if originally one of the assigned pair flew to the unassigned pair. Since we don't know which bird flew (the hatat or the olah) and which bird remained, none of the three birds in the first pair, or the remaining one bird, can be offered. All must be left to die.