'Servant of Christ' in the Bible

For he who was a slave when he was called in the Lord is a freedman of the Lord, likewise he who was free when he was called is a slave of Christ.

Am I now trying to win the favor and approval of men, or of God? Or am I seeking to please someone? If I were still trying to be popular with men, I would not be a bond-servant of Christ.

Epaphras, who is one of you and a bond-servant of Christ Jesus, sends you greetings. [He is] always striving for you in his prayers, praying with genuine concern, [pleading] that you may [as people of character and courage] stand firm, [spiritually mature] and fully assured in all the will of God.