Parashas Behar · Aliyah 6 · Passuk 25:39
Chabad.org — English translation + Rashi
Torah Temimah cites Kiddushin 15a.
English: “You shall not work him with the work of a slave.” Rather with the work of the land, such as plowing and harvesting.
Classical derasha (Bavli Kiddushin).
Permitted labor for an eved ivri is agricultural or other dignified work, not the demeaning personal service of a permanent slave.