1 Timothy 6:2

"And they that have believing masters, let them not despise them because they are brethren, but rather do them service, because they are faithful and beloved partakers of the benefit." As though he had said, If ye are thought worthy of so great a benefit, as to have your masters for your brethren, on this account ye ought more especially to submit. ... And why does he thus command? In the case of unbelievers, naturally, because it would have been unreasonable to address those who would pay no heed to him; but where believers were concerned, what was his reason? Because masters contribute greater benefits to their servants, than servants to their masters. For the former furnish the money to purchase for them sufficient food and clothing; and bestow much care upon them in other respects, so that the masters pay them the larger service, which is here intimated, when he says, "they are faithful and beloved, partakers of the benefit." They suffer much toil and trouble for your repose, ought they not in return to receive much honor from their servants?

"These things teach and exhort." A Teacher has need not only of authority, but of gentleness, and not only of gentleness, but of authority. And all these the blessed Paul teaches, at one time saying, "These things command and teach"; at another, "These things teach and exhort." For if physicians entreat the sick, not for the benefit of their own health, but that they may relieve their sickness, and restore their prostrate strength, much more ought we to observe this method, of entreating those whom we teach. For the blessed Paul does not refuse to be their servant: "We preach not ourselves," he says; "but Christ Jesus the Lord; and ourselves your servants for Jesus' sake"; and again, "All things are yours, whether Paul or Apollos." And in this service he serves with alacrity, for it is not slavery, but superior to freedom. For He says, "Whoever committeth sin is the servant of sin."