Midrash su Deuteronomio 15:16

(Fol. 23) Our Rabbis were taught (Deut. 15, 16) Because he (the servant) is well with thee; i.e., well with food and well with drinks with you (the employer). This means that thou shalt not eat white bread while thy servant eats dark bread; that thou shalt not drink old wine while thy servant drinks fresh wine; that thou shalt not sleep upon cushions while thy servant sleeps on straw. From this, remarked our Rabbis, we may infer that whoever buys a Hebrew slave, it is as if he were buying a master over himself, (Ib. b) (Ex." 21, 6) And his master shall bore his ear through with an awl, etc. R. Jochanan b. Zakkai interpreted this passage in a symbolical way (giving an ethical signification to the Biblical law about perforating the slave's ear). "Why was the ear chosen to be bored, above all the other members of the body? The Holy One, praised be He! said: 'The ear which heard on Mt. Sinai (Lev. 25, 55) For unto Me are the children of Israel servants, but not servants under servants, and this one went and purchased another master upon himself, therefore must the ear be bored for not remembering what it heard."' (Ex. 21, 6) And he shall bring him at the door, etc. Simon b. Rabbi interpreted this in a symbolical way: "Why was the door and the door-post upon which the slave's ear shall be bored chosen in preference to any other place in the house? The Holy One, praised be He, said: 'The door and the door-post which were witnesses in Egypt at the time when I passed over the lintel and the doorposts, when I said, all the children of Israel are My servants and not servants under servants, for which purpose I have also redeemed them from slavery unto freedom, and this one went and bought a master upon himself, therefore shall his ear be bored before the lintel and the door-posts.'"

"I love my master, etc.": This tells me only of one who has a wife and children and his master has children (that his ear is bored). Whence do we derive that if his master does not have a wife and children (that his ear is not bored)? From (Devarim 15:16) "and it shall be, if he say to you, etc." From here it is derived that he is not bored unless both he and his master have wife and children.

R. Simeon the son of Lakish maintained: Shem’s descendants also became slaves, as it is said: And if thy brother, a Hebrew man or a Hebrew woman, be sold unto thee (Deut. 15:12). Shem’s descendants, however, are freed at the expiration of six years, of servitude, as it is written: Then in the seventh year thou shalt let him go free (ibid.), while the descendants of Ham are never freed, as is said: You may hold them to service forever (Lev. 25:46). Therefore, he remains a lifelong slave and does not go forth into the world a free man. Why was this curse imposed upon him? Because he was responsible for his father’s degradation. Thus, the Holy One, blessed be He, brought retribution upon the descendants of Ham by humiliating them by means of the king of Asshur, as it is said: So shall the king of Assyria lead away the captives of Egypt and the exiles of Ethiopia, young and old, naked and barefoot (Isa. 20:4).