It is with great love and care that Paul, the aged apostle, wrote the letter to the Ephesians. Some thirty years prior, the man known as Saul of Tarsus was stopped in his tracks in person by Jesus of Nazareth. This Jesus not only met Saul but he radically changed Saul into a new man. So great was this transformation that not only did his name change, but his whole life trajectory was completely altered. Now Jesus was his life, and the gospel message was his work.
At the heart of Paul's view towards the world was an unswerving passion for all to know and partake of the Jesus who had come to save. It was this obsession with Jesus that led Paul on many trips away from his home to the edges of the known world, and it was this passion that would lead him to found the community of Jesus followers in Ephesus. Followers, though, may not be the best description of what these people were, maybe partakers would be better. Whatever description we would give them, Paul might say that they are in-Christ-ians.
In this letter, Paul's pen is set to say in many ways that all of God's promises and blessings are to be found in Jesus Christ! Put in other words; God has no blessing and promise that can be found outside of Jesus Christ—in him is every spiritual blessing and he himself the gospel (good news). Paul had come to know him as the bread of life and living water, and he takes great care that his fellow saints would know him in like fashion.
Paul wrote this letter while in chains in Rome, some 2,000 kilometres from Ephesus. His letter is a message of encouragement to this growing church located in the busy centre of this city. Ephesus was a port city and a powerful cultural, religious, and political centre. Paul had visited this church at least twice in his missionary and preaching trips and stayed for several years in Ephesus to teach, preach and equip the church with great effectiveness.
It was to Ephesus that Paul sent Timothy as a pastor, and he maintained relationships with the members through messengers like Tychicus (who delivered this letter from Rome to Ephesus). Encouragement and deepening education make up a majority of the content of this letter. Paul has seen this church grow, but he longs for them walk in ever greater faithfulness to God.
Union with Jesus is the main subject of the letter. For Paul, this subject has an ultimate goal and a primary context. God receiving ultimate glory is the goal and living in self-giving community with others is the primary context.
Paul anchors the gracious work of Christ with one reason alone: that God might be praised for his wonderful grace! God is jealous for praise, and He does all things for his glory—five times in the first fifteen verses alludes to this or outright says it! Later, near the middle of the letter, this causes Paul to break out in a song of praise (3:14-21). God's gracious character is so praiseworthy in the mind of Paul that he constantly highlights and celebrates it.
Secondly, the context in which Paul calls the group to follow Jesus’s leading is in community. This community, although made up by individuals, is called to have the total worship of Jesus Christ as its goal and radical self-giving love as its outworking. Paul pulls no punches and brings this reality to bear on the most practical of relationships such as marriage, family, and work. Union with Christ applies to everything!
As Paul writes this letter, he is diligent in constantly calling his brothers and sisters to the union that they share in Jesus Christ by faith in him. At least 25 times in this short letter Paul connects all the riches of God being ours 'in Christ'. John Calvin, who learned from Paul well in this regard, put into words our union with Jesus, and it is a fitting conclusion and summary to Ephesians.
When we seek salvation whole- its every single part is found in Christ, we must beware lest we derive the smallest drop from somewhere else.
If we seek salvation, the very name of Jesus teaches us that he possesses it.
If Spirit-given gifts are sought-in his anointing they are found; strength-in his reign; and purity in his conception; tenderness-expressed in his nativity, in which he was made like us in all respects, that he might feel our pain.
Redemption, when we seek it, is in his passion found; acquittal- in his condemnation lies; and freedom from the curse- in his cross is known.
If satisfaction for our sins we seek- we'll find it in his sacrifice and there is cleansing in his blood.
If it is reconciliation that we need, for it he entered Hades; mortification of our flesh- in his tomb it is laid. And newness of our life- his resurrection brings and immortality as well comes also with that gift.
And if we long to find that heavens kingdom is our inheritance, His entry there secures it now with our protection, safety too and blessing that abound- all flowing from his kingly reign.
The sum of all those who seek such a treasure trove of blessings; these blessings of all kinds is this: from nowhere else than him can they be drawn, for they are ours in Christ Alone.
With that, I invite you to read the letter of splendor that is Ephesians. Come, be a spectator in the theatre of God and watch the glorious irony unfold as Paul, locked in prison, boasts not only untold riches but freedom in that is found alone in Jesus Christ!
 John Calvin, Institutes of the Christian Religion (1559), 2.16.19 Minor wording translated for modern readability.