1 Timothy 6:1-2b

All who are under the yoke of slavery should consider their masters worthy of full respect, so that God's name and our teaching may not be slandered. Those who have believing masters should not show them disrespect just because they are fellow believers. Instead, they should serve them even better because their masters are dear to them as fellow believers and are devoted to the welfare of their slaves. 

All who are under the yoke of slavery should consider their masters worthy of full respect 
Ephesians 6:5-8  Slaves, obey your earthly masters with respect and fear, and with sincerity of heart, just as you would obey Christ. Obey them not only to win their favor when their eye is on you, but as slaves of Christ, doing the will of God from your heart. Serve wholeheartedly, as if you were serving the Lord, not people, because you know that the Lord will reward each one for whatever good they do, whether they are slave or free.

so that God's name and our teaching may not be slandered 
1 Timothy 5:14  So I counsel younger widows to marry, to have children, to manage their homes and to give the enemy no opportunity for slander.
Titus 2:4-5  Then they can urge the younger women to love their husbands and children, to be self-controlled and pure, to be busy at home, to be kind, and to be subject to their husbands, so that no one will malign the word of God.
Titus 2:7-8  In everything set them an example by doing what is good. In your teaching show integrity, seriousness and soundness of speech that cannot be condemned, so that those who oppose you may be ashamed because they have nothing bad to say about us.

Those who have believing masters should not show them disrespect just because they are fellow believers 
Philemon 15-16  Perhaps the reason he (Onesimus) was separated from you for a little while was that you might have him back forever--no longer as a slave, but better than a slave, as a dear brother. He is very dear to me but even dearer to you, both as a fellow man and as a brother in the Lord.

(parentheses are mine)

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