“Subjecting yourselves one to another,” he says, “in the fear of Christ.” For if you submit yourself for a ruler's sake, or for money's sake, or from respectfulness, much more from the fear of Christ. Let there be an interchange of service and submission. For then will there be no such thing as slavish service. Let not one sit down in the rank of a freeman, and the other in the rank of a slave; rather it were better that both masters and slaves be servants to one another—far better to be a slave in this way than free in any other; as will be evident from hence.
Suppose the case of a man who should have an hundred slaves, and he should in no way serve them; and suppose again a different case, of an hundred friends, all waiting upon one another. Which will lead the happier life? Which with the greater pleasure, with the more enjoyment? In the one case there is no anger, no provocation, no wrath, nor anything else of the kind whatever; in the other all is fear and apprehension. In the one case too the whole is forced, in the other is of free choice.
In the one case they serve one another because they are forced to do so, in the other with mutual gratification. Thus does God will it to be; for this He washed His disciples' feet. Nay more, if you have a mind to examine the matter nicely, there is indeed on the part of masters a return of service. For what if pride suffer not that return of service to appear? Yet if the slave on the one hand render his bodily service, and thou maintain that body, and supply it with food and clothing and shoes, this is an exchange of service: because unless thou render your service as well, neither will he render his, but will be free, and no law will compel him to do it if he is not supported.
If this then is the case with servants, where is the absurdity, if it should also become the case with free men. “Subjecting yourselves in the fear,” says he, “of Christ.” How great then the obligation, when we shall also have a reward. But he does not choose to submit himself to you? However do thou submit yourself; not simply yield, but submit yourself. Entertain this feeling towards all, as if all were your masters. For thus shall you soon have all as your slaves, enslaved to you with the most abject slavery.
For you will then more surely make them yours, when without receiving anything of theirs, thou of yourself renderest them of your own. This is “subjecting yourselves one to another in the fear of Christ,” in order that we may subdue all the passions, be servants of God, and preserve the love we owe to one another. And then shall we be able also to be counted worthy of the lovingkindness which comes of God, through the grace and mercies of His only-begotten Son, with whom to the Father, together with the Holy Ghost, be glory, might, honor, now and forever and ever. Amen.
Source: Homilies on Ephesians (New Advent)