John Calvin Commentary 1 Timothy 6:2

"And they that have believing masters, let them not despise them, because they are brethren; but let them serve them the rather, because they that partake of the benefit are believing and beloved. These things teach and exhort." — 1 Timothy 6:2 (ASV)

Who have believing masters The name of brother might be thought to establish equality and consequently to take away dominion. Paul argues, on the contrary, that slaves should more willingly subject themselves to believing masters because they acknowledge them as children of God, are bound to them by brotherly love, and are partakers of the same grace.

It is no small honor that God has made them equal to earthly lords in what is most important, for they share the same adoption with them. Therefore, this should be a significant encouragement to bear slavery with patience.

They are believers and beloved This is an additional argument: slavery is much more easily endured under mild lords, who love us and whom we love in return. There is also the bond of faith, which binds together very closely those who are of different conditions.

These things teach and exhort. He means that these are matters on which he should teach extensively, and he wishes that doctrine should be accompanied by exhortations. It is as if he had said that this kind of instruction should be repeated daily, and that people need not only to be taught but also to be roused and urged by frequent exhortations.