Shevuot (Oaths) 11 - Removing Holiness from Sacrifices
When an object is donated or consecrated to the Temple, it attains sanctity and should not be used for one's own needs. Consecrated objects can be redeemed with money, and the sanctity transfers to money. Higher than this is physical sanctity: if the consecrated object can be used in the Temple service - for example if it is an animal fit for the Altar, wine, flour, or incense - then it cannot, as a rule, be redeemed.
Nevertheless, Ulla said in the name of Rabbi Yochanan that daily offerings that are not needed by the community can be redeemed. There were four such lambs at the end of each Temple's fiscal year, when new half-shekels began to be used.
Here is the procedure. The Temple treasurer borrows some funds, which are thus completely unconsecrated. He redeems the lambs, transferring their holiness to the money. This money is then added to the old half-shekels and is used for plating the Holy of Holies. The treasurer then repurchases the lambs with new half-shekels. Where does their holiness go? The court makes it a condition when consecrating the lambs in the first place that if they are not needed, they can be redeemed.
Art: Pieter Claesz - Still Life with Wine Glass and Silver Bowl