Pesachim 98A

המפריש פסחו ומת, לא יביאנו בנו אחריו לשם פסח אלא לשם שלמים.

With regard to one who separates his Paschal lamb and then dies, his son may not bring it after him for the purpose of a Paschal lamb because it may no longer be used for that purpose after its owner has died. Rather, it is brought for the purpose of a peace-offering.

גמ׳ אמר רב הונא בריה דרב יהושע: שמע מינה תלת. שמע מינה: בעלי חיים נדחין.

Talmud: Rav Huna, son of Rav Yehoshua, said: Conclude 3 halakhot from this Mishnah, concerning one who separates an unfit sheep as a Paschal lamb: Conclude from it that living things can be permanently deferred; not only is a sacrifice that has already been slaughtered permanently deferred, but so is a living animal that has been separated as a sacrifice for which it is unfit. This is clear from the fact that a female animal separated as a Paschal lamb is not offered as a peace-offering, but rather redeemed for money, which is then used for free-will offerings. This Mishnah clearly supports one side of a dispute on this issue in tractate Yoma 63b.

ושמע מינה: דחוי מעיקרא הוי דחוי. ושמע מינה: יש דחוי בדמים.

And furthermore, conclude from this that deferral at the outset, when the lamb is first consecrated, is considered a permanent deferral; even though the female animal was never fit for use as a Paschal lamb and therefore one might have thought that it should be brought as a peace-offering, the fact that it may not be brought as a peace-offering indicates that it has been completely deferred. (See tractate Sukka 33b for an opposing view.) And conclude from this that there is deferral not only with regard to the offering itself, but also with regard to the money of that offering, as the proceeds from the sale of the offering are used for free-will offerings rather than peace-offerings (Rabbeinu Ḥananel).