Leviticus 27:9

כל אשר יתן ממנו EVERYTHING THAT A MAN GIVE implies even the case when he said, “the foot of this animal shall be a burnt offering” his words have binding force). It (the animal) is therefore sold for the purpose of a burnt-offering to one who has to bring such an offering and the monies realized by its sale are חולין (non-holy) and are returned to the owner with the exception of the value of that limb (Sifra, Bechukotai, Chapter 9 1; Arakhin 5a; Temurah 11b; Chullin 69b).

And if it be a beast, of which men bring an offering to the Lord, all that any man gives of such to the Lord shall be holy.

וְאִ֨ם־בְּהֵמָ֔ה אֲשֶׁ֨ר יַקְרִ֧יבוּ מִמֶּ֛נָּה קׇרְבָּ֖ן לַֽיהֹוָ֑ה כֹּל֩ אֲשֶׁ֨ר יִתֵּ֥ן מִמֶּ֛נּוּ לַיהֹוָ֖ה יִֽהְיֶה־קֹּֽדֶשׁ׃