Menahot 48: The Parallel of the Voluntary Peace-offering

The case of slaughtering 4 lambs with the 2 loaves of Shavuot (instead of 2 lambs), then how is that error handled? Two of those lambs are not offered for their own sake, since they aren't presented in the right context, as, for example, a generic peace-offering. That is, the first two lambs have already fulfilled the Shavuot requirement. Also, Rav Yitzhak comes from the land of Israel to the study halls of Babylonia, and he teaches: Animals that are offered for the wrong purpose cannot be used, but must be left to burn... And his rationale for disqualifying these offerings is by virtue of comparison with the sin-offering. Until the Gemara turns the argument on its head and suggests that this mandatory peace-offering is more similar to the voluntary peace-offering, which would leave it a valid offering. Plus, if the animal that is brought is the wrong animal, for example, if it is the wrong age, those are disqualified.