The passage
      v11. Paul begins his final greetings with a word of encouragement:
        i] "Cheer up". The NIV actually has "good-bye", but the word probably means "rejoice" rather than good-bye and is therefore the first of Paul's final exhortations. Christian joy is not exuberance but rather a peaceful sense of Christ's uplifting. It is possible to cry, and at the same time be filled with the joy of Christ, cf. Phil.3:1, 4:4, Gal.5:22.
        ii] "Aim for perfection", or as Phillips puts it, "straighten yourselves out." Paul may be speaking about personal sanctity, but more likely group harmony.
        iii] "listen to my appeal." "Be admonished", "consider carefully the exhortations in this letter", or better, the exhortations of gifted members of the church.
        iv] "Be of one mind", or as Barclay puts it, "agree with one another." Paul is not speaking about rigid uniformity, blind submission to authority, but a unity, an agreement in the essential elements of their faith in Christ, agreement in the truth. Christian unity is essential for the people of God.
        v] "Live in peace", or possibly better, "live at peace with one another." The Corinthian church was marked with disunity, immorality, even civil litigation, and so it certainly needed a little bit of togetherness.
      Paul follows up his exhortations with a divine promise. Our God, who is a God of peace and love, will reside in the midst of a people who seek peace and love. Division drives our Lord away; harmony invites him into our fellowship.
      v12. Paul now encourages his readers to properly greet each other. In their culture, a kiss was the accustomed greeting, but let it be a "holy" one, a pure and sincere one. Paul then follows up with a greeting from the "saints" in Macedonia. The saints, of course, are living believers, not dead believers.
      v13. Paul concludes with a final benediction. This is a Trinitarian benediction in that it speaks of God as Father, Son and Holy Spirit. God's revelation of himself takes place within human experience. Within that experience, the writers of the New Testament came to understand God as a multi-personal being. He is a God who relates within himself. Their experience of God as triune (one God but three persons) was revealed to them in the context of redemption. God's intention to save a people to himself from lost humanity exposed his person as triune. In the context of salvation, the New Testament writers experienced the individuality of each of the members of the Godhead (trinity). Here, in this verse, Paul identifies the persons of the trinity by their different functions within the redemption of humanity. In particular, this triune nature of God is revealed in the grace of Christ. He freely gives his very being for us. In his death we die to sin, in his life we live unto God. Now freely possessing the righteousness of Christ, we may come into the presence of God the Father and possess his eternal and abiding love. Nothing can take his love away from us. He is ours and we are his. As one of the Father's loved ones, we are now possessed by the indwelling Spirit. With the Holy Spirit now infusing our complete self, we become one with the Father and the Son, in fellowship with God, and also through God, with each other.

Be blessed
      There are many things we would like to possess, but then there are some things we need to possess, some things we need "with" us. We need to possess the wonder of God's person. The mystery of God's person is that he is multi-personal. He is one God in three persons. He is a being who relates within himself, a being who is multi-faceted. Although we cannot understand this mystery, we can actually experience it. Our God has revealed himself as three persons, and does so in our experience of salvation.
      We touch Christ in his grace toward us. Day by day we experience his grace in the forgiveness of all our failings - past, present and future. We experience his total acceptance, his victory over sin and death, his empowering to new life, both now and for eternity. All this is ours because of Jesus' death and resurrection on our behalf.
      We touch the Father in his love toward us. He has sent his son to die for us. He has welcomed us into his presence, such that we even now stand before his throne. His love for us is unconditional and not limited by time, circumstance, or even our own sin.
      We touch the Spirit in his gift of fellowship. Through the indwelling Spirit of Christ we are one with all members of the trinity. We are in fellowship with the Father and the Son, through the Spirit. That fellowship extends to all our brothers and sisters in the Lord.
      So, the God that we worship is one God in three persons, a triune God.

v11
      katartizesqe (katarizw) pres. pas. imp. "aim at perfection" - be restored. This is possibly a "be what you are" idea and therefore "aim at perfection" is a reasonable paraphrase. Yet, the verb is passive and therefore, the idea may be of allowing the Spirit of Christ to restore us. So, what we could have here is a "walk by the Spirit" idea.
      parakaleisqe (parakalew) pres. pas. imp. "listen to my appeal" - be encouraged, possibly encourage yourselves. The NIV's "listen to my appeal" goes beyond the text.
      to auto froneite (fronew) pres. imp. "be of one mind" - be of the same mind. "Be harmonious in thought and aim." Plummer.