The recent dapim of our Gemara have been discussing how changes in the name or status of a given object may affect the ownership of that object. Our Gemara raises the question of ye’ush – when an owner despairs of ever receiving an object that was lost or stolen.
Ulla teaches that ye’ush by itself does not create a change of ownership, quoting the passage (Malakhi 1:13) in which the prophet pointedly states that God rejects the offering of a stolen sacrifice, just as He rejects offerings that are physically blemished. Ulla concludes that just as a sacrifice with a physical blemish cannot be fixed in any way, similarly a stolen sacrifice cannot be fixed, indicating that even after the owner’s ye’ush, the animal will still not become the property of the thief.
Tosafot suggest that Ulla’s statement on our page refers specifically to ye’ush on its own, while the other ruling is in a case where ye’ush is accompanied by a change in status.
Rabbeinu Hananel argues that the statement on our page is limited to cases where the thief wants to fulfill a mitzva with the object or bring a sacrifice. In those cases the operating principle that keeps the transfer of ownership from taking place is that it would allow for a mitzva ha-ba’ah ba-aveirah – a commandment that is fulfilled by means of a sinful act.
The commentaries discuss the concept of mitzva ha-ba’ah ba-aveirah at great length. The general conclusion is that not every sinful act connected to a commandment negates the mitzva. When the aveira (transgression) is what allows the mitzva to be performed – as in the case where the animal is to be brought as a sacrifice – then it cannot be used for performance of a mitzva.