Leviticus 25:43

לא תרדה בו בפרך THOU SHALT NOT RULE OVER HIM WITH RIGOUR — i. e. do not force him to do some useless work with the sole purpose of vexing him. Do not e.g. say to him, “Warm me this cup of drink" when this is unnecessary; nor: “Hoe beneath this vine tree until I come" whilst he does not know when you may be expected to come back. Perhaps you will say, “No one knows the fact — whether it is necessary or not, so I will tell him that it is necessary”! — the thing is thus entrusted to his (the master’s) heart only, therefore Scripture states, “but be afraid of thy God!” (Sifra, Behar, Section 6 2; see Rashi on Leviticus 19:32).

לֹא־תִרְדֶּ֥ה ב֖וֹ בְּפָ֑רֶךְ וְיָרֵ֖אתָ מֵאֱלֹהֶֽיךָ׃

Thou shalt not rule over him with rigour; but shalt fear thy God.