כִּ֤י תִקְנֶה֙ עֶ֣בֶד עִבְרִ֔י שֵׁ֥שׁ שָׁנִ֖ים יַעֲבֹ֑ד וּבַ֨שְּׁבִעִ֔ת יֵצֵ֥א לַֽחָפְשִׁ֖י חִנָּֽם׃
Kapag bumili ka ng aliping Hebreo, anim na taon siyang maglilingkod, at sa ikapito ay lalaya siya nang walang bayad.
Sefer HaMitzvot
That is that He commanded about the law of a Hebrew (Jewish) slave. And that is His, may He be blessed, saying, "When you acquire a Hebrew slave" (Exodus 21:2). And [while] most of the laws of this commandment have already been explained explicitly in the Torah, all of the laws of this commandment are explained in Tractate Kiddushin. (See Parashat Mishpatim; Mishneh Torah, Slaves 1.)