Leviticus 27:18

(18) But if he sanctify his field after the jubile.—If, however, the vow is made after the jubile, the priest is to value the field according to the number of years from the time of the vow to the next jubile year.

And it shall be abated from thy estimation.—That is, the years which have elapsed since the last jubile up to the time when he made the vow are to be deducted from the jubile cycle, and hence so many shekels are to be taken off from the original valuation of fifty shekels. Thus, for instance, if he vowed the field at the estimated value of fifty shekels twenty years after the jubile, the priest is only to reckon the thirty years which have to run to the next jubile, and is to deduct twenty shekels for the twenty years which have elapsed since the last jubile. Accordingly, the vower would only have to pay thirty shekels, exclusive of the fifth part above the estimated value.

A Bible Commentary for English Readers, edited by Charles John Ellicott (1878–1897) — public domain. Text from a community e-Sword module.

And if he that sanctified the field shall in any wise redeem it,.... Is desirous of it, and determined upon it at any rate, repenting that he had parted with it in this manner:

then he shall add the fifth part of the money of thy estimation to it: the Jerusalem Targum is, the fifth part of the shekels of silver: that is, if he has a mind to redeem it, and is resolved on it, as soon as he has sanctified it, then, besides the fifty shekels of silver it is rated at, and might be sold for to another, he must pay a fifth part thereof, that is, ten shekels more, for reasons before given, Lev 27:15,

and it shall be assured to him; remain firm and stable with him, abide by him, and he in the possession of it as his property, ever after, as if he had never sanctified it.

John Gill's Exposition of the Whole Bible (1746–1763) — public domain (CC PDM 1.0). Text via the HelloAO Bible API.

After the jubilee, i.e. some considerable time after the jubilee, as appears from the following words.

Unto the year of the jubilee; the defalcation from the full price of fifty shekels being to be more or less, as the years are more or fewer. See Lev 25:15-17.

Matthew Poole's English Annotations on the Holy Bible (1683–1685) — public domain. Text from a community e-Sword/MySword module.

After the jubilee - That is, some considerable time after. The defalcation from the full price of fifty shekels shall be more or less as the years are more or fewer.

John Wesley, Explanatory Notes Upon the Whole Bible (1754–1765) — public domain. Text via the GEBible commentary corpus.

ואם אחר היבל יקדיש BUT IF HE SANCTIFY [HIS FIELD] AFTER (i. e. some years after) THE JUBILEE, — and similarly, of course, if he dedicated it from the year of (i. e. immediately after) the Jubilee, — and in either case it remained for a time in the possession of the treasurer and then this man comes to redeem it some years after the Jubilee,

וחשב לו הכהן את הכסף על פי השנים הנותרת THEN THE PRIEST SHALL RECKON FOR HIM THE MONEY ACCORDING TO THE YEARS THAT ARE LEFT — it must be according to a reckoning. How is it to be done? You see, it (Scripture) has fixed the value of forty-nine years at fifty shekels, that is, one shekel for each year and one additional shekel for all of them (for all the years together). Now a shekel is forty-eight pundion; that gives one selah (shekel) and one pundion for each year, except that there is one pundion short for all the years (reckoning the price per year as the Torah prescribes, he pays forty-nine shekels and forty-nine pundion, equal to fifty shekels and one pundion whereas really he should pay fifty shekels, which is one pundion less than the calculation based upon the yearly rate. Our Rabbis said that that pundion is the commission for the money-changing (Bekhorot 50a), and therefore if he comes to redeem the field some years after the Jubilee, he must give a selah and a pundion for each year of those years that remain until the Jubilee year (Sifra, Bechukotai, Chapter 10 10; Arakhin 24b).

ונגרע מערכך AND THERE SHALL BE ABATED FROM THE VALUATION the number of years that have elapsed from the Jubilee year until the year when the redemption takes place.

Rashi on the Tanakh — English translations: “The Judaica Press complete Tanach with Rashi, translated by A. J. Rosenberg” (CC BY 4.0); “Pentateuch with Rashi's commentary by M. Rosenbaum and A.M. Silbermann, 1929-1934” (public domain); “The Metsudah Tanach series, Lakewood, N.J” (CC BY 4.0); and “The Book of Joshua, Metsudah Publications, 1997” (CC BY 4.0). Text via Sefaria.