Servants were to look on the service to their masters as part of their service to Christ.

 Gr. haplotēs (see on Rom. 12:8). The one aim should be to please Christ in the discharge of duty to the slave master. “Doubleness” of heart would mean seeking to please outwardly while avoiding proper service whenever possible. A slave might be tempted to rationalize that since his servitude was unjust, it was only proper that he should gain his rights by subterfuge if necessary. To do right because it is right is a high Christian principle.

 This is a typical Pauline phrase (cf. 1 Cor. 2:3; 2 Cor. 7:15; Phil. 2:12) connoting great care and earnestness. It is used when a solemn responsibility before God is enjoined, in this case, the servants’ responsibility to have every possible anxiety to please their masters. They were not released by Christianity from their obligations to their legal masters, and should have a deep sense of their duty.

 This phrase, which also appears in Col. 3:22, differentiates between their physical servitude to their masters and their spiritual allegiance to Christ. Human slavery may imprison the body, but it never can subjugate the spirit. Paul is here incidentally declaring the limitations of human slavery, which was able to demand the service of the body but could not command the spirit.

By following Paul’s instruction on their relations with their masters, the large number of Christian slaves within the empire would have a powerful influence on the upper class, who were the slaveowners. Thus, in their own way, the vast number of slaves would form a mission body whose power would be felt throughout society. Inevitably, with slave and master truly brethren, a social and religious revolution would be under way.

 Gr. douloi, “slaves,” “bond servants” (see on Rom. 1:1). This expression is used frequently by Paul both to describe his own relation to Christ and to give counsel concerning the slavery and servitude that existed throughout the Roman world (see 1 Cor. 7:21, 22; Col. 3:22-25; 1 Tim. 6:1, 2; Philemon; 1 Peter 2:18-25). Slavery was anciently practiced, not only by pagans, but also by Christians in the early Christian church. Nowhere in the Scriptures is this unnatural practice specifically condemned, but in both the OT and the NT principles are enunciated that would tend in time to eradicate it (see on Deut. 14:26; 1 Cor. 7:20-24; Philemon).