Winger, Thomas M. "Epistolary Conclusion: Fellowship in Prayer, Commendation, and Blessing: 6:18-24." Ephesians. St. Louis: Concordia Publishing House, 2014, 755-793.
As he closes the letter to the Ephesians, Paul asks that they pray for him. The near synonyms used in 6:18, προσευχή and δέησις, are used in conjunction regularly in terms of the prayers in public worship (Winger 2014, 755). Paul is therefore asking to be included in the prayers when the church is assembled. Though there is no finite verb in verses 18-20, Winger considers there to be a different subject, and that the participle is able to serve as the main verb (Winger 2014, 757). Verse 19 makes plain Paul's intent that when the Ephesians pray he wants them not only to pray for all Christians but to specifically include him (Winger 2014, 759). Paul's desire is that God would give him gifts he needs to carry on his ministry. In particular, he asks that God's Word would speak for him when he opens his mouth and that speech would be bold (Winger 2014, 760). Though Paul is an elder statesman and an ambassador of Christ, he is not free. As he endures imprisonment and eventual trial, he wishes to speak freely as a messenger of the Gospel (Winger 2014, 762).
In Ephesians 6:21 Paul moves on to commend Tychicus to the Ephesians (Winger 2014, 763). Tychicus will let the Ephesians know other things which didn't seem appropriate for inclusion in the actual letter. This was a fairly common expectation. Paul's commendation signifies that Tychicus is someone he trusts entirely, not only as a messenger, but as a faithful servant of Christ, a fellow teacher with Paul (Winger 2014, 764). He is to be received with respect (6:22).
In Ephesians 6:23, Winger observes that Paul repeats "grace and peace" from 1:2, but as "peace and grace," thus creating a chiastic inclusio, signaling the theme of the entire letter (Winger 2014, 766). Verse 24 is more typical of the closing of Paul's letters, as he prays that grace would be with them. However, his mention of them as "those who love our Lord Jesus Christ" is unusual, as it is the only mention of our love for God, rather than God's love for us (Winger 2014, 767). The final words of the blessing, "in incorruptibility," are challenging. Winger considers them unlikely to describe the love of the Ephesians (Winger 2014, 768). He is also not satisfied with the emphasis shifting to the incorruptible nature of the resurrected Jesus (Winger 2014, 769). He concludes it probably refers to the incorruptible nature of the Christian, who dwells in the new life of the baptized.
From a structural standpoint, Winger finds the clear divisions of pericopes which could be discerned early in the letter to be largely absent as it moves to a conclusion. Paul seems to be following a more "continuous flow of thought" by Ephesians 6:18-24 (Winger 2014, 771). Grammatically, though verse 18 is connected to what came before, the actual subject has shifted (Winger 2014, 772).
The conclusion of Paul's letters departs from the pattern we can see in countless Greco-Roman letters (Winger 2014, 772). Winger notes a much more complex formulation used by Paul, containing substantially more elements than found in other authors (chart on p. 773). Winger takes this to be an innovation which influenced many of the New Testament and postapostolic Christian writers (Winger 2014, 774). The elements, taken together, bring the author and recipients into a closer and more personal fellowship than they would otherwise expect.
Ephesians 6:18-20 express a fellowship in prayer between Paul and the Ephesians (Winger 2014, 777). Throughout the letter, prayer has been a significant element. Now, at the conclusion, Paul asks for a continued relationship in prayer. Winger notes that in the earliest Christian practice the corporate prayer of the church was part of the eucharistic celebration. It was not until the Lutheran Reformation that the intercessions were moved to a separate unit of liturgy (Winger 2014, 778-779). Paul's requests for prayer are always focused on his desire that the Gospel would work through him. This is the way he would hope all people would pray (Winger 2014, 780-781).
Ephesians 6:21-22 speak to the fellowship Paul and the Ephesians have through Tychicus, the emissary (Winger 2014, 782). Winger discusses in brief the way letters would be carried at the time of Paul, as well as the related need for letters of introduction and identification of author, courier, and destination. In general, the authoritative letter served as a substitute for the author's actual presence (Winger 2014, 784).
Finally, in Ephesians 6:23-24, Paul expresses a fellowship with the Ephesians as they share in the grace of God. His benediction speaks to their unity. Winger provides a chart of all the Pauline closing benedictions (Winger 2014, 788-789), so as to compare the elements. Grace and peace are the central ideas in all. Winger also notes that the letters all begin and end with grace. All include peace at the start, and more than half include it in the closing benediction (Winger 2014, 790). Winger suggests this may represent an existing liturgical practice, as it is relatively consistent.