Bekhorot 36A

אימר דאמר רבי מאיר לחששא, לאחזוקינהו מי אמר?

The Talmud answers: One can say that R' Meir says that priests are suspect with regard to causing blemishes only to the extent that there is a concern that they might have caused a blemish. But did he say this ruling to establish them as those who definitely cause blemishes? Certainly not.

איבעיא להו: עד מפי עד, מהו לעדות בכור? רב אסי אסר, ורב אשי שרי. אמר ליה רב אסי לרב אשי: והא תנא דבי מנשה: אין עד מפי עד כשר אלא לעדות האשה!

§ A dilemma was raised before the rabbis: With regard to testimony based on hearsay, where one repeats the testimony of another witness, what is the halakha in a case of such testimony about a blemished firstborn animal? Rav Asi deems prohibited the slaughter of the animal based on such testimony, and Rav Ashi deems it permitted. Rav Asi said to Rav Ashi: But isn’t it taught in a baraita in the school of Menashe that hearsay testimony is valid only for the testimony of a woman, where one testifies that her husband is dead? This indicates that such testimony is not accepted in all other instances.

תני: אלא לעדות שהאשה כשרה לה בלבד.

Rav Ashi responded: Emend the baraita and teach it like this: Testimony based on hearsay is valid only for that testimony for which the testimony of a woman is valid. According to Rav Ashi, the baraita is teaching that any case where the testimony of a woman is valid, hearsay testimony is valid as well, and this includes testimony concerning a blemished firstborn animal.

רב יימר אכשר עד מפי עד בבכור, קרי עליה מרימר: ״יימר שרי בוכרא״. והלכתא: עד מפי עד כשר לעדות בכור.

The Talmud relates that Rav Yeimar deemed fit testimony based on hearsay with regard to a blemished firstborn animal. Mareimar condescendingly called him: Yeimar who permits firstborn animals. The Talmud concludes: And the halakha is that testimony based on hearsay is valid in the case of a firstborn animal.