Long ago, the law respecting the idea of sanctuary was embedded in British common law. Fugitives would be immune from arrest in sacred places, such as places of worship. You’ve probably seen a movie where some neer-do-well runs into a church with police on his heels and yells “sanctuary,” as though he’s discovered some trump card against getting caught.
However, sanctuary wasn’t quite the unequivocal boon to absconding felons as it would first appear. If he made it inside a church, the fugitive would then have 40 days to surrender to secular authorities or confess their crimes and be subject to forfeiture of their worldly possessions and permanent exile, i.e., “abjure the realm.”