Pesachim 9:6-7

Pesachim 9:6

Rabbi Yehoshua said, “I learned from my teachers both that an animal substituted for a Passover offering is sacrificed and that an animal substituted for a Passover offering is not sacrificed, and I can’t reconcile these two statements.” Rabbi Akiva explained the situation for him: If one loses his animal for the Passover offering and substitutes another, then the original animal was found before the second was slaughtered, the original is left to graze until it develops a disqualifying blemish. It is then sold and a peace-offering is brought using the proceeds; likewise any animal substituted for it. If the original turned up after the second was slaughtered, it is brought as a peace-offering; likewise any animal substituted for it.

Pesachim 9:7

The Passover offering must be a male animal in its first year. If one designates a female, or an animal in its second year, it is left to graze until it develops a disqualifying blemish. It is then sold and the money is used to give a donation to the Temple. If a person designated an animal for use as the Passover offering and he subsequently died, his son may not bring it as a Passover offering. Rather, he brings it as a peace-offering.