Midrash su Levitico 25:44

3) (Vayikra 25:44) ("And your man-servant and your maid-servant, which will be to you, from the nations, which are around you; of them shall you buy a man-servant and a maid-servant.") Lest you say: If You forbade all of these to us, who shall serve us? It is, therefore, written "And your man-servant and your maid-servant, which will be to you from the nations." What is the intent of this? Whence is it derived that if a Jew lived with his maid-servant and begot a son by her you are permitted to make him your servant? From "which will be to you." "from the nations which are around you": and not from the Canaanites in the land, (whom it is a mitzvah to destroy). "from them shall you buy a man-servant and a maid-servant": "a man-servant and a maid-servant": man-servant is being compared to maid-servant. Just as there is no kiddushin (betrothal) for a maid-servant (with a Jew) (viz. Shemoth 21:4), so, there is no kiddushin for a man-servant (with a Jewess).

"his man-servant or his maid-servant": to make one liable for each in itself. R. Eliezer says: Scripture speaks of a Canaanite (as opposed to a Hebrew) man-servant. You say this, but perhaps it speaks of a Hebrew? (This is not so, for) it is written here "his man-servant or his maid-servant," and elsewhere, (Leviticus 25:44) "From them (the Canaanites) shall you buy a man-servant or a maid-servant." Just as there, the Torah speaks of the Canaanites, so, here. Variantly: man-servant is being likened to maid-servant, and maid-servant to man-servant. Just as "maid-servant" — (she may be sold as a maid-servant,) whether adult or minor, so "man-servant," adult or minor — to exclude a Hebrew man-servant, who although (he may be sold as) a man-servant when he is an adult, may not (be sold as) a man-servant when he is a minor. And to exclude a Hebrew maid-servant, who, although she may be a maid-servant when she is a minor, may not be a maid-servant when she is an adult, (leaving her master, as she does, with the advent of pubertal signs.) R. Yitzchak said: I might understand that (also included is) a servant of two partners or one who is half-free, half-slave; it is, therefore, written "his man-servant or his maid-servant." Just as the first implies a servant that is entirely his, so, the second — to exclude the servant of two partners or one that is half-free (half-slave). R. Yishmael says: Scripture speaks of a Canaanite man-servant, it being written (Exodus 21:21) "for he (the servant) is his money." Just as his money is his for all time and he exercises complete control over it, (so, the servant being spoken of) — to exclude a Hebrew man-servant, who, though under his complete control, is not his for all time, (leaving, as he does in Yovel), and to exclude a servant of two partners or one who is half-free (half-slave), who, though he is his for all time, is not under his complete control.

"the eye of his man-servant or the eye of his maid-servant": to make him liable for each in itself. R. Eliezer says: The verse speaks of a Canaanite man-servant. You say this, but perhaps a Hebrew is intended? It is, therefore, written (Leviticus 25:44) "From them (the Canaanites) shall you buy a man-servant and a maid-servant."