1 I therefore, a prisoner for the Lord, urge you to walk in a manner worthy of the calling to which you have been called – Eph. 4:1
The Ephesians had been called to the faith of Christ, and so their way of life had to correspond to that calling. For that to happen it was necessary for them to consider what the calling was to which they had been called, who had called them, how he had called them and for what purpose. Without working all that out they would not be able to walk in a way that would be worthy of their calling. They had been called when they were still walking in sin, indeed they were dead in sin, cut off from Christ, from the fellowship of the saints and from God himself. Paul wanted the Ephesians to remember that, as he said to them in chapter 2, “Therefore remember that you were once Gentiles; at that time you were without Christ.” Recalling their former lostness and pagan way of life was an easy way to remind them that after they had been called by grace they were expected to live in a different way from the one they had lived in before.
Reformation Commentary on Scripture: Galatians, Ephesians (Downers Grove, IL; IVP Academic; 2012) p. 241.