Matthew Henry on Leviticus 25:23-34

If the land were not redeemed before the year of jubilee, it then returned to him that sold or mortgaged it. This was a figure of the free grace of God in Christ; by which, and not by any price or merit of our own, we are restored to the favour of God. Houses in walled cities were more the fruits of their own industry than land in the country, which was the direct gift of God's bounty; therefore if a man sold a house in a city, he might redeem it only within a year after the sale. This encouraged strangers and proselytes to come and settle among them.