Serving the Lord is holiness. Lest we won't forget the condition, only if we sin not & when one endures persecution to the end then truly he is a servant.
Jn 8:34 Jesus answered them, Verily, verily, I say to you, Whoever committeth sin, is the servant of sin.
Literally speaking, servants do not live in the house forever, they come and go.
Jn 8:35 And the servant abideth not in the house for ever, but the Son abideth for ever.
Jesus being in the house forever must be obeyed by the servant.
Lk 14:23 And the lord said to the servant, Go out into the highways and hedges, and compel them to come in, that my house may be filled.
For you to become servants of anybody, one must give himself to do what his master desire.
Rom 6:16 Know ye not, that to whom ye yield yourselves servants in obedience, his servants ye are whom ye obey; whether of sin to death, or of obedience to righteousness?
No servant therefore can serve two masters: for either he will hate the one, and love the other; or else he will hold to the one, and despise the other. We can not serve God and sin at the same time.
We serve in exchange of something. There is nobody in his righteous mind serving anybody in his whole life for free or in vain.
1 Tim 6:5 Perverse disputings of men of corrupt minds, and destitute of the truth, supposing gain to be godliness: from such withdraw thyself.
1 Tim 6:6 But godliness with contentment is great gain.
1 Tim 6:7 For we brought nothing into this world, and it is certain we can carry nothing out.