And so I am sure that is literally “being sure of this very thing” and may be rendered as “and therefore I am sure of what follows,” or “… this that I am going to say.” It may, however, be better in some languages to combine the first part of verse 6 with the substance of what is referred to, as in Good News Translation. From the context it is clear that the one who initiated the good work among the Philippians and who would carry it to completion is God. Therefore Good News Translation translates explicitly God, who began this good work. The expression good work may refer to the part taken by the Philippians in the work of the gospel, but more naturally it points to the activity of God at the time of their conversion. The outward cooperation in the work of the gospel is, of course, the outcome and expression of the inward change made at the time of conversion.
It may be necessary to restructure rather radically the clause who began this good work in you. The verb began simply indicates an aspect of the more central activity indicated by the noun work. Therefore one may need to render this clause as “who began to work in you in this good way,” or even “… for good.” One may also express the proper relations by a rendering such as “who began to do in you what was good.”
A single Greek word meaning “will complete” (future tense), in combination with a preposition, is rendered in Good News Translation as a verbal phrase will carry it on until it is finished. The verb, as used in this particular context, has the sense of continuance and consummation (Moffatt “will go on completing”; Bruce “will go on bringing it to completion”). It may also be possible to render this verbal clause as “will continue to work in you until he has finished what he has planned,” or “… accomplished his purpose.”
The Day of Christ Jesus is not a reference to the day of one’s death, but to the Parousia, or the return of Christ (Knox the day when Jesus Christ comes), and so Good News Translation capitalizes the word Day. It is the Day of judgment as well as the Day of salvation (1 Thes 1.10). Apparently the early return of Christ is very much in the apostle’s mind as he writes this letter. In some languages literal translation of the Day of Christ Jesus may be quite misleading; one may need to indicate clearly the idea of Parousia and so render this expression as “on that Day when Christ Jesus returns.”
Quoted with permission from Luo, I-Jin. and Nida, Eugene A. A Handbook on Paul’s Letter to the Philippians. (UBS Handbook Series). New York: UBS, 1977. For this and other handbooks for translators see here .