Paul began this epistle with praise (1.3-14) and prayer to God (1.15-23) before discussing what God has done in the church (2.1-22). He will continue to pray for his readers (3.14-21). But first he explains 1) the mystery of God, 2) his role with the mystery, & 3) the church’s cosmic mission.
The Revelation of the Mystery (1-6)
Paul had the mystery revealed to him & he delivered it in this epistle, viz., the union of Jews & Gentiles into one body. The Father (ch.1), the Son (ch.2), & now the Holy Spirit (ch.3).
1For this reason I, Paul, a prisoner for Christ Jesus on behalf of you Gentiles—
For this reason: This phrase is in reference to the foregoing theological ideas just emphasized. As in 1.15, Paul starts a thought but is diverted (v.2-13) by mention, here, of the Gentiles.
I, Paul, a prisoner…you Gentiles: Not just “a prisoner” but literally “the prisoner,” as if there is no other. Paul is in Roman custody, yet he says in truth he is Christ’s prisoner. His imprisonment for (or possibly by) Christ is for the sake of the Gentiles; in fact, it was his preaching to the Gentiles which landed him in prison. He will refer to himself as a prisoner later also (4.1).
It is all in how you look at you circumstances. “One man will regard his prison as a penance; another man will regard it as a privilege. When we are undergoing hardship, unpopularity, material loss for the sake of Christian principles we can either regard ourselves as the victims of men, or as the champions of Christ. Our point of view will make all the difference” (Barclay 142).
2assuming that you have heard of the stewardship of God’s grace that was given to me for you,
Assuming that you have heard: Seems to indicate that the readers were unfamiliar with Paul personally, indicating that this was a circular letter among the churches in the Lycus River Valley. Several scholars do not see doubt, but certainty (i.e. “since…”); they heard from Paul himself.
The stewardship…for you: Stewardship (Gk oikonomian) was used in 1.10 for Christ. Paul had been entrusted with God’s grace which was a gift given to him (see v.7). He served to dispense that grace to the Gentiles through his role as apostle for you, that is, the “nations.”
In a similar fashion, we, brethren, have been entrusted with the grace of God. We have the gospel of grace. We must be faithful stewards of God’s grace by “dispensing” it to those around us (i.e. evangelism).
3how the mystery was made known to me by revelation, as I have written briefly.
How the mystery: The musterion is the eternal counsel of God kept hidden from man for generations until the times had reached their fulfillment (see p.5). Here especially in this context it is closely related to the gospel being for Gentiles as well as the Jews.
Was made known to me by revelation: The mystery was made known to Paul at some point in his past (aorist tense). Perhaps Paul is thinking of when Jesus appeared to him on the road to Damascus and Jesus revealed to him “I am sending you” to the Gentiles (Acts 26.17-18). Cf. Galatians 1.12. The nature of revelation is some truth is uncovered or disclosed by special communication.
As I have written briefly: see 1.9-10. He now expounds upon his brief comments earlier.
None of us had a bright light from heaven blinding us and disclosing some saving secret like Paul did, but we possess the saving secret of God. As the initiated and illuminated of God, we know the mystery of God and can make it known not merely to men but also to spiritual powers in the heavenly places (see verse 10).
4When you read this, you can perceive my insight into the mystery of Christ,
When you read [this]: This is supplied in English for clarity but is lacking in the Greek. When you read what Paul has written briefly (v.3)…
You can…the mystery of Christ: The word musterion is found 21 times in Paul’s literature with 6 of those in Ephesians (1.9; 3.3, 4, 9; 5.32; 6.19). He will explain it fully in verse 6. So Paul is safe in writing that his readers can understand the mystery just as he understands it.
5which was not made known to the sons of men in other generations as it has now been revealed to his holy apostles and prophets by the Spirit.
Which we not…in other generations: The purpose of God has always been the same though man’s knowledge of His purpose has been limited. The revelation of that grand purpose has been gradual; while the mystery may have been revealed in part in the past, now through the apostles and prophets it has been made fully known.
There were glimpses of God’s grand scheme of redemption, but the full glory of His marvelous plan had yet to be made known fully.
As it has now been revealed: What was once concealed has now been revealed by God. Again, God’s purpose to include Gentiles was not unknown entirely in the Old Testament (cf. Gen 12.3; Isa 49.6); but the full measure of God’s toward the Gentiles was not fully known until now.
To His holy apostles and prophets: Like Paul, these New Testament messengers have been entrusted with the sacred secret of the Savior. That the apostles and prophets are holy speaks to the dedication of their lives to and by the will of God (see 1.1).
By the Spirit: The Spirit alone is able to search “even the depths of God” and only He “comprehends the thoughts of God.” But the Spirit is also able to teach in words so that man might understand the mind of Christ (1 Cor 2.10-16).
Why don’t we have modern-day prophets? Barnes explains, “They were persons endowed in this manner [i.e. inspired of the Holy Spirit] for the purpose of imparting to the newly formed churches the doctrines of the Christian system. There is no evidence that this was designed to be a permanent order of people in the church. They were necessary for settling the church on a permanent basis, in the absence of a full written revelation, and when the apostles were away. When the volume of revelation was finished, and the doctrines of the gospel were fully understood, the functions of the office ceased.”
6This mystery is that the Gentiles are fellow heirs, members of the same body, and partakers of the promise in Christ Jesus through the gospel.
This mystery is: These words are provided for clarity. Paul states the substance of the mystery.
Gentiles are fellow heirs: with the Jews, that is. The emphasis here is upon receiving an unearned gift, especially the blessings God has for His people (1.3) and the same inheritance (1.11-14). Note the present tense—Gentile are the following. This is present reality.
Members of the same body: This is a single word in the Greek (susoma) and is unique to Paul later church writers. Literally it is co-body. There is but “one body” (4.4) and both Jews & Gentiles are part of it.
Partakers…through the gospel: The promise most scholars point to is that made to Abraham (Genesis 12.3) and is confirmed in Galatians 3.7-14. “They do not get this blessing indirectly through the Jews, or by becoming Jews, but directly, as Gentiles” (PC 105). Only in Christ Jesus can Jews and Gentiles partake of this blessing; only through the gospel are they invited and admitted.
It is still “through the gospel” that we gain access to the promise, body, and inheritance today. We must believe, accept, and obey “the gospel of your salvation” (1.13) to be incorporated into Christ Jesus. As Christians, we need to value the gospel. “If we do not value the gospel as revelation from God, it will not impact our lives.” Think of the parable Jesus told about the pearl of great price (Mt 13.44-46). We have that which is of ultimate value; it was all Paul and all we have. “We must give attention to the gospel, be defined by the gospel, and solve our problems by applying the gospel.” And the gospel is not merely about getting to heaven; it is about life here and now as well as over yonder. It captures our initial conversion and our daily walk as disciples. It touches on our forgiveness and how we ought to forgive others. It speaks to God’s unfathomable love for us and how we ought to love one another. With so many implications upon life right now, it is no wonder Paul calls it “the unsearchable riches of Christ” (v.8). And then we gather with the saints once or twice a week and think we’ve got it. No, we only start unwrapping the gift here; you take it home and finish the job the rest of the week.
 Snodgrass 169.
 Ibid 170.