The New Testament epistles address servants and masters directly in Ephesians 6 and Colossians 3 and 4.
In Ephesians 6:5:
5 Servants, be obedient to them that are your masters according to the flesh, with fear and trembling, in singleness of your heart, as unto Christ;
In Colossians 3:22:
22 Servants, obey in all things your masters according to the flesh; not with eyeservice, as menpleasers; but in singleness of heart, fearing God:
In Colossians 4:1:
1 Masters, give unto your servants that which is just and equal; knowing that ye also have a Master in heaven.