Even the altar likes dessert TB Makkot 12

Rabbi Shimon doesn’t hold the principal “לֵב בֵּית דִּין מַתְנֶה עֲלֵיהֶן-The court tacitly stipulates concerning them that they should be consecrated for the day on which they are ultimately brought” (Sefaria.org translation) Consequently, any leftover ‘ola sacrifice, a complete burnt offering, can be repurposed as another ‘ola sacrifice. The same is not true with a Khatat sacrifice, a sin offering. It cannot be used as an ‘ola sacrifice. In order to desanctify it and repurpose it as an ‘ola, one must put the animal out to pasture and wait until develops a blemish. Once it has a blemish, it can be redeemed and that money is used to buy ‘olot sacrifices.

Even the altar has a slow “season” when no one is offering up sacrifices. These repurposed ‘olot are offered up on the altar during this slack time so that the altar is constantly being used. These sacrifices are called desserts because they come after “the main meal.”

“Rabbi Yoḥanan explained that Rabbi Shimon holds that lambs that were consecrated for the daily offerings that remain unused at the end of the fiscal year are offered as supplementary offerings. The Gemara notes: This is also taught in a baraita: What type of offerings would they bring from the surplus lambs that were consecrated for the daily offerings? They would bring from them dessert, like white figs, for the altar. The Gemara asks: Are white figs ever offered on the altar? But isn’t it written: “For any leavening or fruit honey you shall not cause to go up in smoke as a fire-offering to the Lord” (Leviticus 2:11)? The term “fruit honey” includes all tree fruits. The Gemara answers: Rav Ḥanina teaches: The supplementary offerings are to the altar like white figs for a person.” (Sefaria.org translation)

Not all animals are eligible to be “dessert.” “The Gemara discusses what may be used for the supplementary offerings: Rav Naḥman bar Rav Ḥisda taught: One does not supplement the offerings of the altar with a bird burnt-offering. Rava said: This ruling is an absurdity [burkha]. Rav Naḥman bar Yitzḥak said to Rava: What is the absurdity? The ruling has a basis. I said this ruling to Rav Naḥman, and said it to him in the name of Rav Shimi of Neharde’a, as Rav Shimi of Neharde’a says: The surplus lambs that were consecrated for the daily offerings are allocated for communal gift offerings, and there is not a bird burnt-offering that is offered by the community.” (Sefaria.org translation) Only bulls, goats, and sheep are offered up as communal gift offerings.