Reference for Chullin 82:25

(ויקרא יח, ג) ובחוקותיהם לא תלכו ואם עשה כן צריך בדיקה אחריו:

THIS IS THE RULE: IF ONE SLAUGHTERED AN ANIMAL DECLARING IT TO BE A SACRIFICE WHICH CAN BE BROUGHT EITHER AS A VOTIVE OR A FREEWILL-OFFERING IT IS INVALID, BUT IF HE DECLARES IT TO BE A SACRIFICE WHICH CANNOT BE BROUGHT EITHER AS A VOTIVE OR A FREEWILL-OFFERING IT IS VALID.

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