The Yovel Year

Ohr Hachayim on Parshas Behar Chapter 25, verse 28 (Free Translation)

וְאִם לֹא-מָצְאָה יָדוֹ, דֵּי הָשִׁיב לוֹ
But if he cannot afford enough to repay him...

This means if they will fear the master because there is no strength in the people to endure any more sufferings, and their heavenly debts are numerous and have overwhelmed them, and he sold himself until the Yovel year which is the time limit for the geulah b'itah (redemption "in it's time")--then he goes out in the Yovel and returns to his inheritance because there is an end to exile even if Israel are complete evildoers, G-d forbid.