"There is one body and one Spirit, just as you were called to one hope when you were called; one Lord, one faith, one baptism; one God and Father of all." (Ephesians 4:4-6)
Paul the prisoner urges the Ephesians to live a life worthy of their calling, with all humility and gentleness, bearing with one another in love, making every effort to keep the unity of the Spirit through the bond of peace. The theological foundation of this unity is sevenfold: There is one body and one Spirit, just as you were called to one hope when you were called; one Lord, one faith, one baptism; one God and Father of all, who is over all and through all and in all. The Catechism identifies this passage as the doctrinal basis of the Church's unity and the ecumenical imperative: the unity of the Church is grounded in the unity of the Trinity, and divisions among Christians wound what God has made one (CCC 813).
But to each one of us grace has been given as Christ apportioned it. Christ gave some to be apostles, some to be prophets, some to be evangelists, some to be pastors and teachers, to equip his people for works of service, so that the body of Christ may be built up until we all reach unity in the faith and in the knowledge of the Son of God and become mature, attaining to the whole measure of the fullness of Christ.
The second half of the chapter turns to ethics. The Gentiles live in the futility of their thinking, darkened in understanding, given over to sensuality and impurity. But that is not how the Ephesians came to know Christ. They were taught to put off the old self, corrupted by deceitful desires, and to put on the new self, created to be like God in true righteousness and holiness. Therefore put away falsehood and speak truthfully. Do not sin in your anger; do not give the devil a foothold. Do not let any unwholesome talk come out of your mouths but only what is helpful for building others up. Get rid of all bitterness, rage, anger, brawling, and slander, along with every form of malice. Be kind and compassionate, forgiving each other just as in Christ God forgave you.
Brothers and sisters, do not give the devil a foothold. The foothold is always something small: the unresolved anger of sunset, the bitterness nursed overnight, the unkind word that opened a crack. Paul's instruction is precise: do not let the sun go down while you are still angry. Tonight, before sleeping, close every crack. Forgive whatever needs forgiving. Give the devil no overnight accommodation.
Lord God, one body, one Spirit, one hope, one Lord, one faith, one Baptism, one Father of all. Build up your Church in the unity that reflects your own. And in our daily lives, let us put off the old self and put on the new, forgiving as we have been forgiven. Through Christ our Lord. Amen.