The Lord
Lord — Master and rightful ruler; in Paul's letters the title of the risen Jesus, carrying the weight of the divine name
I therefore, the prisoner of the Lord, beseech you that ye walk worthy of the vocation wherewith ye are called, Ephesians 4:1
Paul is in chains because he serves the Lord Jesus Christ; he elsewhere calls himself 'the prisoner of Jesus Christ'.
- the same title in Ephesians 3:1 — 'Paul, the prisoner of Jesus Christ' — the same self-description naming Him
