Deuteronomy 23:15-16

Thou shalt not deliver unto his master the servant which is escaped from his master unto thee:

Thou shalt not deliver unto his master the servant which is escaped - evidently a servant of the Canaanites, or of some of the neighbouring people, who was driven by tyrannical oppression, or induced with a view of embracing the true religion, to take refuge in Israel. Such a one was not to be surrendered by the inhabitants of the place where he had fled for protection.

Among the Greeks and Romans slaves were not allowed the privilege of any sanctuary: their master might pursue them any or everywhere; and when he caught the runaway, he branded him with a red-hot iron (Xenophon, 'Mem.,' 2: 10, secs. 1, 21; Florus, 2:, p. 19). But in ancient Palestine, and under the law of Moses, a refugee, the moment he set foot upon the soil, found a secure asylum, and was allowed to settle at pleasure in any part of the land, as in Britain now (Michaelis).