פירוש על ויקרא 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).

'כל אשר יתן ממנו לה, if he had declared it sanctified, without specifying beyond this,

“The foot of this [animal] is a burnt-offering,” his statement is binding. But not so regarding the evaluation of a person since we require something on which life depends, because it is written “souls” regarding a person. But here it is written “any of it that he will give,” to include whatever he dedicates as becomes dedicated.