Paul, a a δοῦλος of Jesus Christ, called to be an apostle, separated unto the gospel of God...
(Rom 1:1)
δοῦλος:
1) a slave, bondman, man of servile condition
1a) a slave
1b) metaphorically, one who gives himself up to another's will those whose service is used by Christ in extending and advancing his cause among men
1c) devoted to another to the disregard of one's own interests
2) a servant, attendant
(Thayer's)
And in the other sense:
Verily, verily, I say unto you, Whosoever commits sin is the ??????? of sin. And the ??????? abides not in the house forever: but the Son abides ever.