Halakhah su Levitico 27:21

He prohibited us from redeeming unspecified dedications of land. And that is His saying, "it shall not be sold and it shall not be redeemed" (Leviticus 27:28). And the language of the [Sifra] (Sifra, Bechukotai, Chapter 12:4) is, "'And it shall not be redeemed' - by the owner. What shall he do with it? 'To the priest shall be his holding' (Leviticus 27:21). Or this is perhaps [the law] even if he stipulated, 'to the Lord.' [Hence] we learn to say, 'it.'" And the laws of this commandment - meaning, the fields dedicated to the priests - have already been explained in Tractate Arakhin. And there (Arakhin 28b), it is said, "Dedications to the priests do not have redemption, but must be given to the priests, like the priestly tithe (terumah)." (See Parashat Bechukotai; Mishneh Torah, Appraisals and Devoted Property 6.)

That is that He commanded us to administer the laws of dedications. And that is that when anyone dedicates something of his and says, "This is dedicated," that thing is given to a priest - though if he specified that it would be for Temple upeep, it will be for Temple upkeep - since undifferentiated dedications are for the priests. And that is His, may He be exalted, saying, "However, any dedication that a man will dedicate, etc." (Leviticus 27:28). And the hint to us about undifferentiated dedications being for the priests, is its being stated (Leviticus 27:21), "like a field that was dedicated, it shall belong to the priest." And the regulations of this commandment have already been explained in the eighth chapter of Arakhin and the first chapter of Nedarim. (See Parashat Bechukotai; Mishneh Torah, Appraisals and Devoted Property 6.)

From the laws of the commandment is that which our Rabbis, may their memory be blessed, said (Mishneh Torah, Laws of Appraisals and Devoted Property 6:4) that one who dedicates to the Heavens consecrates [the property], but he [may] redeem it for its worth, such that the value goes to upkeep of the [Temple] and the property goes out to the non-sacred. But dedications of the priests never have a redemption. Rather behold they belong to the priests and their children forever. And [in the case of] a priest who got the rights for a field of dedication and sold it, it goes back to him or his seed in the Jubilee; as is is stated (Leviticus 27:21), "for the priest shall it be a holding" - this teaches that his field of dedication is like a field of holding for an Israelite. And the rest of its details and of its content - all of it is like I wrote above (Sefer HaChinukh 357) and it is all elucidated in Tractate Arakhin. And there is no doubt that these two negative commandments - which are "it shall not be sold" and "it shall not be redeemed" - are practiced today according to the opinion of Rambam, may his memory be blessed, as I wrote above: [In the case of] one who dedicates land or movable objects outside the Land at this time, it is given to the priests. [This is so] even though the field of dedication is not practiced in the Land [of Israel] today, but only at the time that the Jubilee is practiced. So did Rambam, may his memory be blessed, write in the Book of Separation (Mishneh Torah, Laws of Appraisals and Devoted Property 8:11-12).