We are in Tractate Bechoros, chapter 5, Mishnah 4. The first part of the Mishnah continues and summarizes what we learned in the previous Mishnah: a kohen who intentionally inflicted a blemish on his bechor is not permitted to rely on this blemish to slaughter the animal, and he must wait until a new blemish develops on it. Now the Mishnah comes to discuss a case where the blemish was created unintentionally.
"Hayah bechor rodfo":
The Mishnah deals with a kohen whose bechor animal chased after him, and out of self-defense he struggled with it, kicked it, and in the process gouged out its eye or caused it another blemish. The animal indeed became blemished, but the kohen did not intend to inflict a blemish on it in order to permit it for eating. In such a case the Mishnah states: "Hayah bechor rodfo, uvaato veasah bo mum - harei zeh yishachet alav" - if a bechor was chasing him, and he kicked it and made a blemish on it, he may slaughter it on account of it. The kohen is permitted to slaughter the bechor based on this blemish, because it was not created with malicious intent but rather incidental to his self-defense.
As we will see later, testimony is required to confirm that this indeed happened; but once the kohen obtains this testimony, he is permitted to slaughter the animal, since he had no intention to inflict the blemish.
The Shulchan Aruch goes so far as to say: a person whose cow chased him in the morning and he escaped it by climbing a tree, and in the afternoon, out of anger that it forced him to climb the tree, he took a stick and struck it in its face, and in the process unintentionally hit its eye and blinded it - even in this case he is permitted to slaughter the cow. Although he himself blinded the animal, his intention at the time of the action was not to create a blemish that would permit it to be slaughtered, but solely to vent his anger on it. Even though this is not proper behavior, and it may involve tzaar baalei chayim (cruelty to animals), nevertheless the blemish was not inflicted intentionally, and therefore he is permitted to slaughter the animal based on it and eat it.
Requirements for Testimony - Background:
The second part of the Mishnah moves to a new topic: the requirements for the testimony confirming that the blemish was caused unintentionally. First, the background must be understood. Every kohen who receives a bechor has a huge incentive to slaughter it as quickly as possible. As long as the bechor is in his possession, and the Beis Hamikdash is not standing or the kohen is living in the Diaspora and cannot offer it, it is incumbent upon him to feed it and care for it every day, which involves time and money. The sooner he slaughters the animal, not only will he gain meat to eat or sell, but mainly he will stop the continuous bleeding from his bank account, a situation that could last for years.
Because of this, the Sages said that a witness is required to testify that the blemish that was created did not come from a deceitful act of intentional blemish infliction. The question is who is qualified to serve as this witness.
The regular rule in questions of issur veheiter (prohibitions and permissions), such as whether a certain food is permitted to be eaten, is that one person is sufficient, and he does not need the regular halachic status of a witness: it can be a woman, a relative, and even someone who is personally involved in the matter. If a man's daughter tells him that the food is kosher, he is permitted to eat from it. There is no need for official supervision; it is enough that someone testifies that they supervised the item and that it is kosher. (This is not the place to go into the laws of kashrus, which are more complex, but this is the main rule.)
However, there are people who have the status of a "chashud" (suspect), meaning that they are suspected of disregarding the halachah and violating it. At the end of the mishnayos in the previous chapter, we saw a case of someone who was suspected regarding maasros (tithes), Sheviis (the Sabbatical year), or bechoros, and there it was explained that the definition of a suspect is someone who has a proven track record - he was caught in the past violating the rules. However, there are entire categories in which Chazal established that any person belonging to them is considered a suspect, because this is common in practice. Therefore, Chazal said that kohanim are all suspected of intentionally inflicting blemishes in order to permit bechoros for eating, and once they are considered suspects, they are no longer qualified for testimony.
Three levels of personal involvement in the matter:
His own animal: Here his involvement is absolute. His strong desire is to slaughter the animal to be rid of its expenses, and he is certainly a suspect.
Another kohen's animal: Seemingly he has no personal gain here, and we have the rule "ein adam choteh velo lo" - a person does not commit a sin when he gains nothing from it, for he loses much and profits nothing. However, there is still a concern of collusion, which is the concern of "gomlin" (reciprocity) - you scratch my back and I'll scratch yours: kohen A will testify that the blemish on kohen B's animal occurred by chance, and in return kohen B will testify about kohen A's animal.
Only general involvement: A kohen who has a herd of bechoros and handed it over to a non-kohen shepherd to care for them. Even the shepherd has a certain involvement: he thinks that if he benefits his kohen employer, he will receive a raise in salary or a piece of the meat. The question is whether we suspect a Yisrael to lie in matters of bechoros in exchange for such a small favor.
The approaches of the Tanaim in the Mishnah:
The Mishnah opens: "Kol hamumin hare'uyim lavo bidei adam" - any blemish that could have been caused by an intentional act, such as an animal that was blinded in one eye, where there is room for suspicion. In contrast, a blemish that cannot be caused by a human being, such as an animal born with five legs, does not arouse suspicion at all; whereas an animal missing a leg at least carries the suspicion of an intentional act. In such cases, the Tanaim disagree:
The Tanna Kamma: "Ro'im Yisrael ne'emanim vero'im kohanim einam ne'emanim" - a shepherd who is not a kohen and who works for a kohen master is believed to say that the blemish occurred by chance. Even though he has a certain bias, since he expects some benefit in return, a person will not commit such a severe sin for a minor benefit. However, shepherds who are kohanim are not believed, and not only due to bias, but due to the concern of mutual favors - that kohanim will look out for one another, with one lying for his friend and his friend lying for him.
Rabban Shimon ben Gamliel: "Ne'eman hu al shel chaveiro ve'eino ne'eman al shel atzmo" - his approach is more lenient: The kohen is not believed regarding his own firstborn animals, but he is believed regarding the firstborn animals of another person. In his opinion, we do not suspect bias, just as we do not suspect it with an Israelite shepherd, and we also do not suspect a conspiracy of mutual favors, since a kohen will not lie for another person's animal; the suspicion does not reach that far.
Rabbi Meir: "Hechashud al hadavar lo dano velo me'ido" - this principle was already seen at the end of the previous chapter. Someone who is suspected regarding a specific mitzvah, just as kohanim are suspected regarding firstborns, cannot serve as a judge in that matter and can never serve as a witness for it. Consequently, the testimony of kohanim is not accepted regarding firstborns and their blemishes at all, and in practice, Rabbi Meir agrees with the Tanna Kamma: an Israelite shepherd is believed, and a kohen shepherd is not believed.
The Gemara asks: If Rabbi Meir agrees with the Tanna Kamma, what is he coming to teach? It answers that Rabbi Meir maintains that regarding firstborns, due to the high suspicion of deceit, one witness is not enough and two witnesses are required. Even though generally one witness is believed regarding prohibitions, and in regular matters of prohibited foods, such as kashrut, one witness is sufficient, Rabbi Meir holds that here two are required. Practically, the halachah does not follow this opinion, and one witness is sufficient.
Practical Halachah:
The halachah regarding firstborns follows the lenient approach of Rabban Shimon ben Gamliel: We do not suspect mutual favors, nor do we suspect bias in the matter. Therefore, one witness is sufficient, and even a kohen testifying about the firstborn of another kohen is believed, as we do not assume a person will lie for such a minor matter. This rule applies even to a household member, such as a son who will be invited to the meal once the firstborn is slaughtered - even he is believed to testify that his father's firstborn was blemished by chance. The only ones who are not believed are the owner himself, the kohen, and his wife, since a man's wife is considered like himself and her status is like his. Aside from them, the halachah relies on anyone.
Resolving the Difficulty:
There is a seeming difficulty, since the rule follows the words of Rabbi Meir, that one who is suspected regarding a matter may neither judge it nor testify about it, and someone with the status of a suspect is not fit to testify. Why, then, are kohanim permitted to testify about firstborns, when they are suspected regarding them? (This is the reason that at the end of the previous chapter, the discussion was deferred to here.)
Many explain that there is a distinction here. By Torah law, it is forbidden to inflict a blemish on consecrated animals, as was seen earlier - the offering must be unblemished, and one may not intentionally inflict a blemish on it, and this is one of the 613 mitzvot for which the transgressor receives lashes. However, once the animal becomes blemished, for example, if a person cut the ear of the firstborn - the cutting itself was a Torah transgression, but from then on, by Torah law the animal is blemished and it is permitted to slaughter and eat it.
It was the Sages who said that even though it is permitted by Torah law, it is forbidden by rabbinic law, in order to prevent deceit and to distance a person from the prohibition of inflicting a blemish on consecrated animals. It turns out that our entire discussion in the Mishnah, whether the blemish was caused intentionally or inadvertently, is solely a rabbinic matter, since even if it was caused intentionally, by Torah law it is permitted to slaughter the firstborn and eat it. For this reason, the halachah rules leniently like Rabban Shimon ben Gamliel in everything regarding testimony on firstborns, and relies on any kohen for this, excepting only the owner himself.
In contrast, in other halachot that are certainly by Torah law, the rule applies that one who is suspected regarding a matter may neither judge it nor testify about it, and we do not accept him for testimony in that matter. There, it is not speaking specifically of a case where he has bias; rather, even when he has no bias at all, he is not relied upon in a matter where he is suspected, because the suspicion is general and does not stem only from the bias in this specific case.
In summary: In this Mishnah we learned that a firstborn that chased after its owner and became blemished out of self-defense - it may be slaughtered because of it, since the blemish was not inflicted intentionally, and the same rule applies even when the blemish was caused while venting anger. We also discussed the requirements of testimony: Due to the kohen's financial interest, the Sages established that a witness is required; the Tanaim disagreed whether a kohen shepherd is believed regarding his friend's animal, and the halachah was ruled like Rabban Shimon ben Gamliel that one witness is sufficient, and even a kohen and any household member are believed, except for the owner and his wife. The foundation of this leniency is that the prohibition in this case is solely rabbinic, since by Torah law, an animal that became blemished is permitted to be slaughtered and eaten.