Ephesians 4 turns from what God has done to how His people should live. I therefore, the prisoner in the Lord, beg you to walk worthily of the calling with which you were called. Paul names the qualities this requires: lowliness, humility, patience, and bearing with one another in love. Unity matters because God is one. Paul repeats the word one seven times: one body, one Spirit, one hope, one Lord, one faith, one baptism, one God and Father of all.
Yet unity is not sameness. To each one of us, the grace was given according to the measure of the gift of Christ. He gave some to be apostles; and some, prophets; and some, evangelists; and some, shepherds and teachers. Their purpose was for the perfecting of the saints, to the work of serving, to the building up of the body of Christ. A mature church is not tossed back and forth and carried about with every wind of doctrine. Instead, speaking truth in love, we may grow up in all things into him who is the head, Christ.
Paul then contrasts two ways of life. Some Gentiles walked in the futility of their mind, being darkened in their understanding. But you didn't learn Christ that way. Believers put away the old man and put on the new man, who in the likeness of God has been created in righteousness and holiness of truth. Paul gives practical commands about honesty, anger, work, and speech. Don't grieve the Holy Spirit of God. Let all bitterness and anger be put away. The chapter ends with this charge: And be kind to one another, tender hearted, forgiving each other, just as God also in Christ forgave you.