Commentaire sur Le Lévitique 25:25

כי ימוך אחיך ומכר AND IF THY BROTHER BE WAXEN POOR AND HAS SOLD AWAY [SOME OF HIS POSSESSION] — The introductory words teach us that one is not permitted to sell his real estate except under the pressure of poverty (cf. Sifra, Behar, Chapter 5 1).

כי ימוך אחיך ומכר מאחוזתו, "If your brother becomes poor and has to sell part of his heritage, etc." This paragraph contains cardinal moral-ethical lessons to mankind. Kohelet 10,18 alludes to this when he says: "through slothfulness the ceiling sags." Our sages in Taanit 7 comment on this "you have made "poor" the One of Whom it is said (Psalms 104,3) "המקרה במים עליותיו" "Who sets the rafters of His lofts in the waters;" When people who dwell in the lower parts of the universe stray from the correct path they cause the beneficial outpourigs from the upper part of the universe to cease. They thereby endanger the continuous presence of sanctity on earth. In the final analysis the fate of the universe is determined by the conduct of the creatures who inhabit earth, i.e. "the lower world."

כי ימוך אחיך ומכר מאחוזתו, “When your brother becomes impoverished and sells you a part of his inherited land, etc.” The introduction to this legislation teaches that one does not have the right to sell the land one has inherited in Eretz Yisrael from one’s forefathers except when in economic distress. In addition the Torah teaches that even if one is forced to sell, one should retain at least part of one’s holding.