As a segue from the discussion of someone who sanctified his field in the Land of Israel, the final perek of Massekhet Arakhin discusses the general sale of real estate in Israel. Although this topic is not actually an issue of sanctity, nevertheless there are similarities between these issues.
The Torah explains that someone who sells an ancestral field is permitted – and, in fact, commanded – to redeem the field from the purchaser. Whether or not he does so, the field will automatically be returned to the original owner at the end of the 50-year Jubilee cycle. For this reason, all land purchases in Israel were viewed as short-term sales, and in the event that the original owner chooses to redeem the land from the purchaser, he does it by subtracting the years that field was in the hands of the purchaser and paying the remainder of the purchase price of the field.
The Mishna teaches that the seller must leave the field in the hands of the purchaser for at least two years before he can redeem it. The Sefer HaḤinnukh suggests that the Torah wanted to discourage the original owner from selling his ancestral field easily. If he thought that he could redeem it at any time, he would not be discouraged from selling it. The Ḥinnukh further suggests that this rule applies only to a sale of the field. In the event that he gave it away as a gift, he could redeem it at any time.
In his Mishneh Torah (Hilkhot Shemitta VeYovel 11:18), the Rambam rules that once the two years are up, the original owner can force the purchaser to sell the field, even if he does not want to do so. This would be true if his relatives came to redeem it on his behalf, as well.