Musar zu Dewarim 23:16

The law forbidding extradition of a Gentile slave who fled from his master to the land of Israel (23,16) is based on the fact that once one has attained a higher level of sanctity – in this case being present in the Holy land – one has begun to serve the Lord and must not revert to serving man. The slave in question has to be given his freedom; the freed slave will undertake to recompense his erstwhile master for his financial loss. The entire legislation demonstrates the advantages of ארץ ישראל and its elevated status. The expression לא תסגיר includes not forcing the freed slave to live in a walled city with a gate, or under some kind of house-arrest similar to that of the involuntary murderer in a city of refuge. He is to live wherever it suits him, where he finds work –except in Jerusalem – which is not a city belonging to any one of the tribes. The words באחד שעריך preclude this freed slave from taking up residence in Jerusalem.