2,996. Twice-Consecrated Animals
Hilchos Arachin Vacharamin 6:7
If a kohein sells a field that had been cheirem and the buyer consecrates it, it’s as if he consecrated acquired real estate and it goes back to the kohein who sold it in yoveil. This is so even if the one who bought the field was the one who had proscribed it in the first place. Real estate or movable goods belonging to kohanim or Leviim cannot be proscribed, as per Leviticus 25:34: “Because it is an eternal inheritance for them.” While this refers to fields, it is also applied to their movable property when it comes to proscription based on Leviticus 27:28: “from all that he owns... and from his hereditary field.”
Hilchos Arachin Vacharamin 6:8
If someone consecrated animals for the altar and then he consecrated them for Temple upkeep, that second consecration is effective. The animal is appraised and redeemed, and its value is given towards Temple upkeep, after which the animal is offered for the purpose of its original consecration. However, if someone takes an animal that had been consecrated for Temple upkeep and he consecrates it for the altar, such as for a burnt offering or a peace offering, or if he proscribes it for the kohanim – in such cases, his act is ineffective. This is because once an animal has been consecrated for Temple upkeep, it can no longer be consecrated for the altar or proscribed. It no longer belongs to him, and a person can’t consecrate something that isn’t his.