Ex 21:26 "If a man hits a manservant or maidservant in the eye and destroys it, he must let the servant go free to compensate for the eye. 27 And if he knocks out the tooth of a manservant or maidservant, he must let the servant go free to compensate for the tooth.
Reformed thinkers have always looked to God's law to learn general equity, principles of right that apply always and everywhere. As Paul showed, the general equity of a law is not limited only to the immediate subject of a precept of the Law. Thus, he shows in 1 Cor 9:9-10 that a law providing for the care of oxen may also teach us today a general equity for people, particularly their right to enjoy a share of the produce of their labor:
For it is written in the Law of Moses: 'Do not muzzle an ox while it is treading out the grain.' Is it about oxen that God is concerned?" Surely he says this for us, doesn't he? Yes, this was written for us, because when the plowman plows and the thresher threshes, they ought to do so in the hope of sharing in the harvest. 11 If we have sown spiritual seed among you, is it too much if we reap a material harvest from you?
Though I understand that the immediate subject of a Mosaic precept and the ultimate reach of its equity might be far apart, I had never considered how the equity of the Mosaic law of slavery might be applied in other areas.
Samuel Rutherford, however, in his Lex Rex, Q. 4, offers an interesting perspective on the general equity of the Mosaic laws regulating the treatment of slaves in the context of the limitations on government and the obligation of lesser magistrates to vindicate the people from the tyranny of their superiors. Alongside considerations of the duties of children to parents and freedmen to their patrons, he asks whether the obligations of subjects to their rulers could be greater than that of servants to their master?
In the light of precepts like those set forth in Exodus 21:26-27, he argues that if even a bond servant has the right to freedom after receiving a substantial injury from his master, then a people -- even if we were to think of them as the slaves of their rulers -- should also be relieved of their obligations to their rulers if they are substantially injured by tyranny. Of course, he argues the relative status of a subject in relation to a ruler is higher than that of a slave to a master. Therefore, he concludes that the servant's right to freedom after substantial injury belongs more strongly to a free people injured by its rulers.
Rutherford finds the same equity exemplified in Roman law:
... there was a proviso in Roman law that a slave whom his master did not tend in illness should be regarded as free. And what is even more important, a slave is by a provision of the written law free to accuse his master of high treason. But who is more liable to this accusation than the tyrant who openly subverts all rights divine as well as human? But, you will rejoin, before whom shall he be accused? I answer, either before those who since they possessed the authority to elect him, also possess the authority to judge him, or before those who are the chief defenders of the supreme power and from whom there is no appeal.
Similarly, although under Roman law, freedmen owe every respect to their patrons, so much so that in ordinary law they can institute only civil actions against them, yet for special reasons, that is if they have suffered some terrible injustice at the hands of their patron or have caught him in adultery with their wives, they can in virtue of the civil law lay a capital charge against him.
My purpose with these arguments is not to tighten the conscience (of men) by means of the civil laws or the pronouncements of philosophers as if by most reliable rules, but only to show as clearly as may be how unjust is the opinion of those who would leave men no means at all by which they may avail to break the onset of imminent or openly aggressive tyranny, however cruel and unjust the matter might be.Rutherford's argument suggests a broader rule. Principles of justice concerning those of the lowest status set forth general lower limits on the rights of all. The formal end of slavery does not mean that the precepts of the Mosaic law do not continue to illuminate universal rights. Rather, God uses discussions in the Mosaic law of examples pertaining to those with the least legal status, e.g., oxen and slaves, to underscore the minimum rights pertaining to all.