As Revised Standard Version shows, the verse is an incomplete sentence in Greek; Good News Translation has added pray to God at the end of the verse in order to complete the sentence (similarly Translator’s New Testament, New English Bible, and others); some translations have ellipses at the end of the verse (Jerusalem Bible, Traduction œcuménique de la Bible) or a dash (Revised Standard Version, New International Version, and others); New American Bible reverses the order of verses 1 and 2. What Good News Translation has done is to establish the relationship between verses 1 and 14, to keep the reader from being confused by an incomplete sentence at the beginning of the section.
For this reason refers back to the exposition (2.11-22) of the reconciliation between Jews and Gentiles effected by Christ and points forward to the prayer (3.14-21); in verse 14 For this reason picks up the thought broken by the digression in verses 2.1–3:13.
Some languages have no convenient transitional device such as For this reason, and the only effective equivalent is a clause, for example, “Because of what God has done” or “Because of what God has done in bringing Jews and Gentiles together as one.”
I, Paul: this is emphatic; some languages will say “I myself, Paul” to express the same emphasis.
The prisoner of Christ Jesus: Good News Translation is not good; the meaning is “I am a prisoner because I serve/belong to Christ Jesus” (see similar expression in Philemon 1, 9). Prisoner here is meant literally of physical imprisonment, not figuratively of the writer’s complete submission to Christ’s will (see also 4.1 and 6.20).
It may also be possible to translate the prisoner of Christ Jesus as “a prisoner because of what I have done for the sake of Christ Jesus,” or “I am in prison because I serve Jesus Christ.” There is, however, a problem in some languages in having a kind of triple apposition, namely, I, Paul, the prisoner of Christ Jesus. This must be broken up in some languages to read “I, Paul, who am a prisoner for Christ Jesus’ sake.” In order that people may understand that prisoner is not to be taken in a figurative sense, one may translate I, Paul, the prisoner of Christ Jesus as “I, Paul, am in prison because of Christ Jesus.”
For the sake of you Gentiles: this is a further reason; Paul is a servant of Christ Jesus working for the good of the Gentiles. So the two phrases might be rendered: “I am a prisoner because as a servant of Christ Jesus I work on your behalf,” or “I am a prisoner because I serve Christ Jesus and work on your behalf.”
Quoted with permission from Bratcher, Robert C. and Nida, Eugene A. A Handbook on Paul’s Letter to the Ephesians. (UBS Handbook Series). New York: UBS, 1982. For this and other handbooks for translators see here .