Comentario sobre Exodo 21:2

כי תקנה עבד עברי IF THOU BUYEST AN עבד עברי — This means a servant who is a Hebrew. Or perhaps this is not so, but it means a servant of a Hebrew (one who had been the servant of a Hebrew), i. e. a Canaanitish servant whom thou hast bought from an Israelite, and it is with regard to him that Scripture states “six years he shall serve”! — And if you ask, how I will then explain the commandment, (Leviticus 25:46) “and you shall leave them (the Canaanitish servants) as an inheritance for your children [and they shall serve you forever]”? then I reply, that this refers to the case of a Canaanitish servant who has been bought from a heathen; but if such a servant has been bought from an Israelite he shall go free at the end of six years! — This explanation that our text refers to a Canaanite servant will not hold, for Scripture states, (Deuteronomy 15:12) “and if thy brother an Hebrew man be sold unto thee [and serve thee six years, then in the seventh year thou shalt let him go free from thee]” — the Torah says, as it were, by using the two terms העברי and אחיך: I tell you this (that the servant shall go free in the seventh year) only with regard to thy brother! Consequently Leviticus 25:46 has to be applied to any Canaanite servant, whether bought from a Hebrew or from a heathen and עבד עברי in our text can only denote עבד שהוא עברי. (Mekhilta d'Rabbi Yishmael 21:2:2)

IF THOU BUY A HEBREW SERVANT. G-d began the first ordinance with the subject of a Hebrew servant, because the liberation of the servant in the seventh year contains a rememberance of the departure from Egypt which is mentioned in the first commandment, just as He said on it, And thou shalt remember that thou wast a bondman in the land of Egypt, and the Eternal thy G-d redeemed thee; therefore I command thee this thing today.²¹Deuteronomy 15:15. It also contains a remembrance of the creation, just as the Sabbath does, for the seventh year signals to a servant a complete rest from the work of his master, just as the seventh day of the week does. There is in addition a ‘seventh’ amongst the years, which is the jubilee, for seven is the chosen of the days [to be the Sabbath], and of the years [to be the Sabbatical year], and of the [seven] Sabbaticals [to be the jubilee]; and they all point to one subject, namely, the secret of the days of the world — from bereshith (in the beginning) till vayechulu (and they were finished).²²Genesis 2:1. See Ramban Vol. I, pp. 61-64. Therefore this commandment deserved to be mentioned first, because of its extreme importance, alluding as it does to great things in the process of creation.²³Ramban’s reticent and challenging language is illuminated in an essay by I. Weinstock (B’maglei Haniglah V’hanistar, pp. 151-241) where he traces the development of this Cabalistic doctrine: The universe is subject to cycles of seven thousand years; after each six thousand years of growth and activity the seventh thousand is one of “rest” — destruction. This process repeats itself seven times — representing a total of forty-nine thousand years, the fiftieth thousand being the jubilee when all existence returns to its beginnings. This phenomenon applies to the planet on which we live as well as to the worlds above us. One can thus get a glimpse into the meaning of Ramban’s words before us, that this commandment “alludes to great things in the process of creation.” This is why the prophet Jeremiah was very stringent about it and said, Thus saith the Eternal, the G-d of Israel: I made a covenant with your fathers;²⁴Jeremiah 34:13. At the end of the seven years ye shall let go every one his manservant, and every one his maidservant.²⁵Ibid., Verses 14 and 10 (Ramban combined here parts of these verses). And on account of its violation, G-d decreed the exile,²⁶Ibid., Verses 17-22. just as the Torah decreed exile for the Sabbatical rest of the land which was not observed,²⁷Leviticus 26:34-35. as I will yet write,²⁸Ibid., 25:2. with the help of the Rock.
When He finished stating the ordinance of this [first] commandment as it applies to Hebrew servants, He began the ordinance of the commandment, Thou shalt not murder,²⁹Above, 20:13. since it is the worst [sin] and then [He stated the ordinances of the commandments] to honor one’s parents, and of Thou shalt not steal,²⁹Above, 20:13. and then He went back to the ordinance of one who smites his fellow-man but did not kill him,³⁰Further, Verses 18-19. and then to the murder of a bondman, which is worse than the killing of an offspring,³¹See further Verse 22 — that for killing an unborn child a fine is paid, while in the case of the bondman, if he did not survive for twenty-four hours after he was struck by the master, the master is liable to death (Verses 20-21). and after that to [injury to] the limbs of Israelites and bondmen,³²Ibid., Verses 24-27. and then to cases of death inflicted by cattle which cause injury.³³Ibid., Verses 28-32. All the sections are thus arranged in logical sequence and in proper order.

כי תקנה עבד עברי, "When you purchase a Jewish slave, etc." Perhaps the meaning is: "when you are about to buy a slave, buy a Jewish slave (rather than a Gentile)." You should not buy a Gentile because you know you can keep him indefinitely.