Sefer HaChinuch ספר החינוך

That owners that dedicated land not sell it, but that it rather be given to the priests: That one should not sell a dedicated field, and so [too,] all other lands. And the law is the same for movable items that have been dedicated by their owners. Rather, they should be given to the priests of that watch, as we wrote in this Order, positive commandment 6 (Sefer HaChinukh 357). And it is even forbidden for the owners to sell it to the treasurer of the consecrated, but rather [the latter] should attain the rights to it with nothing. As God gave the rights of dedications to the priests. And this is with undifferentiated dedications, as we said above. Since it established for us [that the law is] like the [opinion] that says, undifferentiated dedications — meaning to say that one who dedicated but did not specify to whom — are for the priests. As if he dedicates explicitly for the upkeep of the [Temple], the priests do not get rights to [it]. And about the dedications of the priests is it stated here (Leviticus 27:28), “any dedication [...] shall not be sold.” But the priests can certainly sell them according to their will. As [with] the dedications of the priests — after they have gone out from the hand of their owners who dedicated them and have reached the hand of the priests — behold they are like the non-sacred for all of their purposes, as it is stated (Numbers 18:14), “Every dedication in Israel shall be for you.” But so long as they are still under the hand of the owners, it is stated about them (Leviticus 27:28), “every dedication is holy of holies to the Lord.”

And the root of the commandment and all of its content is written above (Sefer HaChinukh 357). See there, “as it is close.” (See Mishneh Torah, Laws of Appraisals and Devoted Property 6.)