לזכות ידיד נפשי האהוב ר' אברהם יצחק בן אסתר וכל משפחתו לברכה והצלחה בכל מעשי ידיהם
The Gemara
The gemara in Bechoros [3b] relates that Rav Mari bar Rochel had a herd of animals and he would sell the ears of the animals to an idol worshipper [so that the firstborns would be patur from the chiyuv of bechor because the ownership of a goy patters] and nevertheless he forbade the animals in shearing and working as a bechor is and would also give them to a kohen lest he "commit an offense" [תקלה].
What was the offense, shearing and working or shechting?
According to Rashi, the offense was that someone would either work with them or shear them. Rabbeinu Gershom learns differently and says that he was concerned that they would be shechted under the assumption that they were chullin so he sold the ears to the kohen and thus would avoid איסור if the animal was shechted.
Why would Rav Mari shecht his bechoros?
Rabbeinu Geshom is very difficult to understand. Rav Mari was the owner of the animals and knew that some of them were bechoros and would definitely not shecht them. And other people would not shecht an animal that doesn't belong to them - so what it the problem?
Jews answer a question with a question - Is a beheima of hefker chayav in bechora?
The Turei Even asks about this story with Rav Mari - Why did he trouble himself by selling them to a goy and not just make them hefker? It must be that an animal that is hefker is still chayav in bechora. However the Tosefta [פרק ב' דבכורות] says that בהמת המדבר is פטור from בכורה and בהמת המדבר is a בהמה of hefker.
Uh oh!
So by golly, why didn't Rav Mari just make his animal ownerless??
The mehalech to explain Rav Mari - A Jew may take control of it and it will thus be holy and he will mistakenly shecht it
Maybe we can suggest as folllows: The gemara in Nedarim [13a] says that even though an animal is holy automatically it is still a mitzva to to sanctify it with one's mouth. The Mekor Baruch [1/24 see there] says that even though a bechor is automatically holy [and one need not verbalize the sanctification], nevertheless there is an איסור of בל יחל דברו if he uses it for his own purposes.
The Maharit Algazi [פרק קמא דבכורות] is מחדש that the תוספתא that says that an animal that is hefker is pattur from the בכורה is referring to an animal that has no potential to become קדוש because it has no owner. BUT, if it later owned by a Jew, it automatically becomes holy [כל הראוי לבילה אין בילה מעכבת].
Maybe Rav Mari didn't want to be מפקיר the animals because in order to do so he would have to remove them from his property [שו"ת חת"ס יו"ד שט"ז] and he was concerned that when he did so a Jew would find them and take them for himself resulting in automatic בכור status [unbeknownst to him] and would then shecht the animal [which is אסור].
That is the explanation of the opinion of Rabbeinu Gershom - He was bothered by the kashya of the Turei Even, why Rav Mari didn't just render his animal hefker and he therefore answered that he was concerned that someone would find it [at which point it would become automatically holy] and shecht it.
Stay tuned - I hope more to come...
[עפ"י שארית יוסף להרה"ג ר' שלמה וואהרמן זצ"ל ח"ז סי' ס"ו]
