Rashi on Leviticus 25:28/רש"י על ויקרא כ״ה:כ״ח

1די השיב לו [BUT IF HE IS NOT ABLE] TO RESTORE IT (lit., if his hand find not sufficient means to restore to him) — Therefore it follows that he (the vendor) has no right to redeem his property in parts (lit., by halves) (Sifra, Behar, Chapter 5 5, Arachin 30a).

2עד שנת היובל UNTIL THE YEAR OF JUBILEE — “until” but not “including” the year of the Jubilee; it means that nothing of time shall have entered into that year (that not one moment of that year shall have passed), because the Jubilee effects the release of such property at its very beginning (in contrast to the cancelling of debts in the “Shemittah” which takes place only at the end of the year; cf. Deuteronomy 15:1 ff.) (Sifra, Behar, Chapter 5 6; Arakhin 28b).