The letter to the Ephesians encourages slaves to see themselves as “slaves of Christ” who “render service with enthusiasm” for the Lord rather than their human masters (Eph. 6:6–7). The fact that their work is for Christ will encourage them to work hard and well. Paul’s words are therefore a comfort when masters order slaves to do good work. In that case, God will reward the slave (Eph. 6:8) even if the master doesn’t, as is typically the case with slaves (Luke 17:8).
But why would slaving away for an earthly master necessarily be “doing the will of God” (Eph. 6:6)? Surely a master could order a slave to do work that is far from the will of God—abusing another slave, cheating a customer, or encroaching on someone else’s fields. Paul clarifies, “Slaves, obey your earthly masters with fear and trembling, in singleness of heart, as you obey Christ” (Eph. 6:5). Slaves can only do for their masters what could be done for Christ. If a master orders slaves to do evil work, then Paul’s words are dreadfully challenging, for the slave would have to refuse the master’s orders. This could lead to unpleasant consequences, to say the least. Nonetheless, Paul’s command is inescapable. “Render service . . . as to the Lord, and not to men and women” (Eph. 6:7). The Lord’s commands supersede the commands of any master. Indeed, what else could “singleness of heart” mean, if not to set aside every order that conflicts with duty to Christ? “No one can serve two masters,” said Jesus (Matt. 6:24). The punishment for disobeying an earthly master may be fearsome, but it may be necessary to suffer it in order to work “as to the Lord.”