Negative commandment · Lo Ta’aseh #257 of 613
Not to have a Hebrew servant perform servile tasks
שלא לעבוד בעבד עברי כעבודת עבד
The verse · Vayikra 25:39
וְכִי־יָמוּךְ אָחִיךָ עִמָּךְ וְנִמְכַּר־לָךְ לֹא־תַעֲבֹד בּוֹ עֲבֹדַת עָבֶד
“And if thy brother who dwells by thee be grown poor, and be sold to thee; thou shalt not compel him to serve as a bondservant:”
The Rambam’s words
Not to have a Hebrew servant perform servile tasks, as [Leviticus 25:39] states: "Do not work him like a slave."
שלא לעבוד בעבד עברי כעבודת עבד, שנאמר "לֹא תַעֲבֹד בּוֹ עֲבוֹדַת עָבֶד" (ויקרא כה, לט).
Why · Sefer HaChinuch #344
That we not make a Hebrew slave perform demeaning work, like the work of a Canaanite (gentile) slave
“It is from the roots of the commandment [that it is] so that a person place upon his heart that our nation is the most honored of all of them.”
Who & when
“And [it] is practiced by males and females at the time that the Jubilee is practiced; and I have already written when the Jubilee is practiced at the beginning of the Order (Sefer HaChinukh 330).”
Where in the Mishneh Torah
Hilchot Slaves הלכות עבדים