And they that have believing masters, let them not despise them, because they are brethren. — This being in servitude to Christian masters, of course, in the days of St. Paul would happen less frequently. Let those Christian slaves who have the good fortune to serve “believing masters” allow no such thoughts as, “Shall I remain my brother’s slave?” take root in the breast and poison the life-work. Let them not presume on the common brotherhood of men in Christ, on their being fellow-heirs of heaven, and on this account deem their earthly masters their equals, and so refuse them the customary respect and attention. Let them remember that, though in heaven there would be no respect of persons, on earth the old class differences were not removed.
But rather do them service, because they are faithful and beloved, partakers of the benefit. — The Greek here is better translated thus: but the rather serve them, because believing and beloved are they who are partakers of their good service. Let these slaves of Christians rather (or, the more) serve their masters zealously and loyally, because the masters who will profit by their true faithful service are themselves believers in Jesus, the beloved of God. This thought should never be absent from the heart of a Christian slave to a Christian master. “Every good piece of work I do will be a kindness shown to one who loves my Lord.”