[If] one slits the ear of a bechor, it may never be slaughtered; [these are] the words of R’ Eliezer. The Sages [however,] say: When it develops another blemish, he may slaughter it on its account. It happened with an old ram with dangling hair [that] a questor spotted it. He said, “What is the reason for this?” They said to him, “It is a bechor, and it may not be slaughtered unless it has a blemish”; [whereupon] he took a dagger and slit its ear. The matter came before the Sages, and they permitted it. [When] he saw that they had permitted [it], he went and split the ears of other bechoros, and they prohibited [it]. Once children were playing in the field, and they tied the tail of lambs one to another. The tail of one of them was torn off, and it was found to be a bechor. The matter came before the Sages, and they permitted it. [When] they saw that they had permitted [it], they went and tied together the tails of other bechoros, and they prohibited [it]. This is a rule: Whatever is [done] with knowledge is prohibited, and without knowledge is permissible.

[If] a bechor was pursuing him, and he kicked it and inflicted a blemish upon it, he may slaughter on account of it. [For] all blemishes that can be inflicted by man, shepherds [who are] Yisraelim are believed, but shepherds [who are] Kohanim are not believed. Rabban Shimon ben Gamliel says: He is believed concerning his friend’s [bechor], but he is not believed concerning his own. R’ Meir says: One who is suspected concerning a thing may neither judge nor testify about it.

A Kohen is believed to say, “I showed this bechor [to an expert] and it is blemished.” All are believed concerning the blemishes of the maaser [offering]. [If] a bechor’s eye was blinded, its foreleg cut off, [or] its hind leg broken, it may be slaughtered by the decision of three laymen. R’ Yose says: Even if there are twenty-three, [it] may not be slaughtered except by the decision of an expert.

[If] one slaughters a bechor and sells it, and it becomes known that he did not show it [to an expert], what they ate, they ate, and he must return their money to them; and whatever meat they did not eat must be buried, and he must return the money to them. Similarly, [if] one slaughters a cow and sells it, and it becomes known that it was a tereifah, what they ate, they ate, and [he] must return the money to them; and whatever meat they did not eat they return to him, and he must return the money to them. [If] they sold it to non-Jews or gave it to dogs, they must pay him [only] the worth of a tereifah.