Комментарий к Эрахин 9:4

ואחד הנותן במתנהn – if he wanted to redeem [the house] within its year, he can redeem, but if not, it is permanently sold to him.

If the [last] day of the twelve months has arrived and it was not redeemed, it becomes his permanent [possession].
This applies whether he bought it or received it as a gift, as it is said: “beyond reclaim” (Leviticus 25:30).
In earlier times, he [the buyer] would hide on the last day of the twelve months, so that [the house] might become his permanent [possession].
Hillel enacted that he [the seller] could deposit his money in the chamber and break down the door and enter, and that the other [the buyer], whenever he wanted, might come and take his money.
Section one: If the last day of the twelve months passes and the owner doesn’t redeem his property, the house becomes the permanent possession of the purchaser. The house doesn’t go back to its original owner during the Jubilee year.
Section two: Leviticus 25:30 reads, “If it is not redeemed before a full year has elapsed, the house in the walled city shall pass to the purchaser beyond reclaim throughout the ages.” The words “beyond reclaim” and “throughout the ages” seem to be redundant. The rabbis use this redundancy as a source from which to conclude that the same laws that apply to selling the land also apply to giving it away. One who gives his house to another can redeem it, although all he must do is claim it in return.
Section three: Before Hillel, the seller would have to actually find the purchaser in order to redeem his house. It seems that they would quite frequently they would wait until the last possible day to redeem the house. This led to the purchaser hiding from the seller so the latter couldn’t reclaim possession of his house. In order to fix this problem, and to allow the sellers, who were assumedly poor and in desperate need of money, to reclaim their homes, Hillel allowed them to deposit their money in the chamber of the treasury in the Temple. Then he could go back to his house, break down the door and enter legally. The purchaser could come and collect his money from the Temple whenever he wanted.
We should note that there are other “takkanot” (rabbinic enactments) that are ascribed to Hillel in which we find Hillel shaping the halakhah to improve the lot of the poor. The most famous of them is the “prozbul” which allowed a creditor to collect his debt after the sabbatical year. There too Hillel acted to protect the poor, for if creditors could not be assured of their ability to collect their loans, they would never lend to the poor in the first place.

היה נטמן (was hidden, hide oneself) – the purchaser on the [exact] day of twelve months in order that the seller not find him to give him [back] his money so that it will be permanently sold to him.

שהיא חולש – that he would put his monies in the chamber of that which is dedicated to sacred purposes in the Temple courtyard.

ויהא שובר את הדלת – of the house of that he sold and enter it. [The word] חולש / assign (his redeeming money to the Temple by depositing there , to assert his privilege of redemption) is like (Isaiah 14:12):”[How are you felled to earth,] O vanquisher of nations!”