Halakha Ulangan 23:16: Mishneh Torah, Negative Mitzvot & Sefer HaChinukh

Not to surrender a slave, who has fled to the land of Israel, to his owner who lives outside Palestine, as it is said, “Thou shalt not deliver unto his master, the servant (who is escaped from his master unto thee)” (Deut. 23:16).

Not to treat a Hebrew servant rigorously, as it is said, “Thou shalt not rule over him with rigour” (ibid. 25:43).

Not to turn over a slave that fled from his master: That we have been prevented from returning a slave that fled from his master outside of the Land, [who came] to the Land of Israel. (See Sefer HaMitzvot, Negative Commandments 254.) And even if his master is an Israelite, we do not return [the slave] to him. But [rather], we free him and write down his value as a debt on himself. And about this is it stated, (Deuteronomy 23:16), “You shall not turn over a slave to his master.” And so is it elucidated in Tractate Gittin 45a, that the verse is speaking about a slave that fled from outside of the Land to the Land of Israel. And they said there that the law about him is that we write a contract with his value [as a debt] for him and we [also] write a contract of [his] freedom; and that we not return him to slavery in any way — since he entered the chosen valley of purity to serve God, may He be blessed, there.