Deuteronomy 23:15, 16
15. Thou shalt not deliver unto his master the servant which is escaped from his master unto thee:
15. Non trades servum domino suo, qui se ad te eripuerit a domino suo.
16. He shall dwell with thee, even among you, in that place which he shall choose in one of thy gates, where it liketh him best: thou shalt not oppress him.
16. Tecum habitabit in medio tui, in loco quem elegerit in una urbium tuarum prout placuerit, nec vim inferes ei.
Although this Law has a tendency to humanity and kindness, it still does not appear to be altogether just. Since many masters oppressed their slaves with tyrannical arrogance, their wickedness rendered it necessary to afford some alleviation to the poor creatures. Thus slaves were permitted to take refuge in temples, and at Rome at the statues of the Caesars, so that if they proved themselves to have been treated with injustice and inhumanity, they might, when their case was proved, be transferred by sale to merciful masters. This, indeed, was endurable, but the refuge which is here granted to slaves defrauds their masters of their just right; since, without their case being heard, they have liberty given them to reside in the land of Canaan; thus, too, the law of nations is violated, since the land is opened to every fugitive. Besides, since runaway slaves are generally wicked and criminal, whatever place may be their asylum, it will be filled with many sources of infection. I know not whether there is sufficient foundation for the opinion of some who think that the slaves were exempted by privilege from their former servitude,1 in order that they might give themselves up to God's service, and that thus true religion might be propagated. It certainly does not seem consistent that filth and refuse of every sort should be received into the Church, because, in the end, it would have been filled with all kinds of corruptions; and besides, it was by no means decorous that whatever crime had been elsewhere committed should be sheltered under God's name. For, suppose a thief, or an adulterer, or a murderer, should leave his master, and seek for an asylum in the Holy Land, what else would it have been to receive and protect such guests, but to overthrow law and justice, and to set up a state of foul barbarism? I think, therefore, that more is to be understood than the words express, viz., that, if it should be found that the slaves had not fled in consequence of their own evil doings, but on account of the excessive cruelty of their masters, the people should not drive them away, which would have been tantamount to giving them up to butchery. And, in fact, it may be inferred that judicial proceedings were to be instituted, because a choice is given as to the city in which they prefer to dwell.
Religion, indeed, stood them in some stead, because those who sought a place and home in the land of Canaan, were obliged to dedicate themselves to God, and to be initiated in His worship; still, God would never have allowed His name to be profaned by the reception of wicked persons without discrimination. Wherefore, as I briefly slated before, God inculcates humanity upon His people, lest, by the extradition of fugitive slaves, they should be necessary to the cruelty of others; because their masters would have been their executioners; and, since lie forbids the people from ill-treating them, He implies, by these words, that He only so far provides for the safety of these wretched beings, as to allow them to defend their innocence in a court of justice; wherefore I have thought fit to place this law amongst the Supplements of the Sixth Commandment.
1 "The Chaldee addeth, a servant of the peoples, i.e., of the Gentiles, who for the religion of God cometh from his master to the Church of Israel. This servant that fleeth to the land (of Israel) he is a righteous stranger, (that is, a proselyte come unto the faith and covenant of God,) saith Maimony." -- Ainsworth in loco.