On the
previous page, we saw that while bringing a Passover offering, one must have the right intention in mind. We also saw that if one changes from the right intention to the wrong one, he invalidates the offering. The question that remained was this: when did he change his mind? For example, when he said, "This is a Passover offering, a peace offering," did he change his mind during a single service, such as the slaughter of the sacrifice, or did he think or talk about Passover offering during slaughter and about peace offering during subsequent walking to the Altar with the blood in the vessel?
This depends on how we understand his statement, "This is a Passover offering, a peace offering." If we take both parts of his statement seriously, we say that he really wanted to change his mind. He, therefore, invested the sacrifice with both qualities. Since this is impossible: it's either Passover or peace offering, he ruined it completely - at least, as far as offerings are concerned. Practically, the animal has to graze in the pasture until it accidentally gets some blemish (for example, in the foot or tail), making it invalid as a sacrifice, and then it is sent home. That is actually the view of Rabbi Yosi.
But if we say that we only listen to the first part of what he is saying, and do not recognize the second part of his statement, then the animal is still a valid sacrifice. The change of mind must have happened on another step of the service. That would agree with Rabbi Meir's view.
The Talmud tries to decide when he changed his mind - completely inside a certain step of the service or between two steps - and remains unable to do so.
Art: The Return of the Flock by Anton Mauve