Comentario sobre Levítico 25:30

וקם הבית...לצמתת (THEN THE HOUSE… SHALL BE ESTABLISHED ABSOLUTELY [TO HIM THAT OBTAINED IT] — i. e. it leaves the control of the vendor for ever and stands under the exclusive control of the purchaser.

Under the control of the buyer. I.e., even though it was in the hands of the buyer [beforehand], it was also under the control of the seller because he could still redeem it. [But now] it remains in the hand of the buyer, as the seller can no longer take it from his hand. Re’m writes: You might ask: [Why does Rashi [say that “it will remain” refers to “its purchaser”]? Why does he not explain that “it will remain” refers to “in perpetuity,” that until now it was only acquired for a year in the purchaser’s hand, [but now it is acquired forever]? It seems that Rashi deduces this since it is written “in perpetuity to its purchaser.” “Its purchaser” is apparently superfluous as it is obvious that this refers to the purchaser. Thus, one can deduce from [the superfluous] “to its purchaser,” that the verse means “for its purchaser and not for its seller.” I.e., until now, the seller had the right to redeem it, but now, after the year has passedt, it left the jurisdiction of the seller, etc.

שנה תמימה, “a full year.” In the event that this particular year was declared a leap year, this works to the advantage of the person wishing to redeem it. (Sifra)