Israelites were not to return self-emancipated formerly enslaved people to their enslavers.
No qualifications are placed on this absolute command to harbor and protect formerly enslaved people who escape. The formerly enslaved person is to settle in a place of her or his own choosing. No one is to mistreat the person based on their former enslaved status. Earlier, Deuteronomy gave provision for people remaining in slavery if they chose to (Deuteronomy 15:7). That seems to have been an anomaly. On this other end of the spectrum, if someone chose not to fulfill the period of indentured servitude, or a captive escaped their Israelite or foreign slave-master, the person was to be protected and treated as anyone else.