Midrash su Levitico 25:39

1) (Vayikra 25:39) ("And if your brother grows poor with you, and he is sold to you, do not work with him the work of a servant.") Whence is it derived that one is not permitted to sell himself and place (the proceeds) in his money-bag to buy animals, vessels, or a house unless he became impoverished? From "And if your brother grows poor and he is sold" — He may not sell himself unless he becomes poor. And whence is it derived that when he is sold, he shall be sold only to you (and not to a gentile)? From "and he is sold to you." And whence is it derived that if beth-din sell him they sell him only to you? From (Devarim 15:12) "If there be sold to you." "your brother": You shall treat him as a brother. I might think that he should conduct himself as a brother; it is, therefore, written "a servant." I might think that you shall also conduct yourself to him as a servant; it is, therefore, written "your brother." How so? You conduct yourself to him with brotherhood (i.e., you call him "brother"); he conducts himself to you with servitude (he calls you "master").

(Exodus 21:2) "If you buy a Hebrew man-servant": Scripture here speaks of one sold by beth-din (to pay for what he has stolen), in which instance he serves both the father and the son. __ But perhaps it speaks of one who sells himself (because of poverty)? (This is not so, for (Leviticus 25:39) "And if your brother grows poor with you, and he is sold to you" speaks of one who sells himself. How, then, am I to understand "If you buy a Hebrew man-servant"? As referring to one who is sold by beth-din because of his theft, that he serves the master and his son.

"Six years shall he serve": I might think (that he performs) both demeaning and non-demeaning service. It is, therefore, written (Leviticus 25:39) "Do not have him work the service of a slave" — whence they ruled: He should not wash his feet or tie his sandals or carry his clothing to the bath-house or gird his loins for an ascent or carry him in a litter or in a chair or in a sedan-chair, as slaves do. Whence is this derived? From (Ibid. 46) "And in your brothers, the children of Israel, one may not lord it over another." But with his son and his disciple, it is permitted.