G‑d permitted the Jewish people to sell their fields in the Land of Israel only if they were in dire financial straits. Furthermore, if a relative of the seller has the financial means to buy back (“redeem”) the sold field from the buyer, he is allowed to do so. As long as at least two years have elapsed since the sale, the buyer may not refuse to sell the land back.
We are G‑d’s Partners
וּבָא גֹאֲלוֹ הַקָּרֹב אֵלָיו וְגָאַל אֵת מִמְכַּר אָחִיו: (ויקרא כה:כה)
[G‑d instructed Moses to tell the Jewish people,] “The redeemer [of the field], who is related to [the seller], may come forth and redeem that [land] which his relative had sold.” Leviticus 25:25

The laws of redeeming land prior to the Jubilee year are based on the principle given two verses ago (Leviticus 25:23): “The land must not be sold [in such a way as] to sever it [permanently from its original owner], for the land belongs to Me.” The prohibition of a permanent sale reminds us that the land ultimately belongs to G‑d; we should never consider ourselves its true owners.

The same applies to whatever wealth or property we may accrue during our lifetimes. “The earth and its fullness are G‑d’s.”1 We should never lose sight of the fact that G‑d has given us whatever we possess only as His partners, in order to refine it, elevate it, and transform it into His true home.2