Besides the fact that such behavior is inherently right, of course, most commentators believe that Onesimus’ return to Colossae with Tychicus (Col. 4:7–9) is one of the reasons why Paul in Colossians 3:22–25 emphasizes the need for slaves to do a good job and work unto the Lord. As we will see in a few weeks, Onesimus was a slave who had wronged his master, Philemon, and the apostle was asking Philemon to show clemency (Philem. 8–16). Such a plea for mercy could have been seen as an excuse for slaves to wrong their masters through indolence and other transgressions — if Philemon could do it with impunity, why not them? Paul’s instructions on the duties of slaves remind them that one cannot take mercy and grace for granted, especially when one knows better, as the Christian slaves in Colossae did.
Yet the apostle does not lay duties only upon slaves in his epistle to the Colossians, but also upon slavemasters. Today’s passage tells us that Paul expected slavemasters to treat their slaves “justly and fairly” (Col. 4:1). Such sentiments were not altogether unheard of in that day, but they were definitely the exception and not the rule. The great philosopher Aristotle, for example, saw no need to speak of justice in the ancient master-slave relationship. In keeping with Old Testament teaching, however, slavemasters in the covenant community were required to do right by their slaves and act in accord with God’s standards for how people should be treated (Ex. 20:8–10; 21:20, 26–27). This is what the Greek term dikaios, which in this context is translated “justly,” means here. Slaves had to be treated like human beings and with the fairness that a free person would expect in Roman society. The slave owed obedience to his master, but the master also owed a debt to the slave — a debt of kindness, justice, and fairness. John Calvin writes, “Masters have not their servants bound to them in such a manner as not to owe something to them in their turn.”
Again, Paul’s statement in Colossians 4:1 radically restricts the power the slavemaster has over the slave. Simply put, the master cannot treat his slave in any manner he likes. This is grounded in the fact that the slavemaster himself is not as free as he might think but has a “Master in heaven.” Christ sees how His people treat those under their charge and holds them to the highest standards.
By way of application, those who are managers or who otherwise supervise people should keep in mind the principle behind the proper treatment of slaves by masters. Employees are not to be regarded as mere cogs in a machine, and Christian supervisors must treat them as people with real needs, hopes, and desires, and not simply as those whose only value is how much they add to or take away from the bottom line.