Philippians 1:6

Textus Receptus:
πεποιθως αυτο τουτο οτι ο εναρξαμενος εν υμιν εργον αγαθον επιτελεσει αχρις ημερας ιησου χριστου

King James:
Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ:

Comments:
Being confident: The meaning of the word used here (not the syntax) implies that Paul has been persuaded to a point of confidence and trust. In other words, his statement to the Philippians is not simply a personal opinion, not even a strong one, but a state of belief to which he has been brought by God. That state of mind is defined by the second participle qualifying the thanks he gives in verse 3. In this case the point is that one of the things that explains Paul's thankfulness to God is his knowledge that God will finish the work he began in the Philippians. Believers ought to be grateful that their salvation is not in their own hands, but in God's. 1 Thessalonians 5:23-24.

he which hath begun a good work in you: Of course God's work of salvation begins long before the specific object of salvation even exists, as Romans 8:29-30 makes clear. But since this work is begun "in you" he is either speaking of the beginning of their experience of faith (the day of their conversion) or of the beginning of the work God did to bring them to a point of faith (their calling to salvation through general then specific grace). Either way, the point which can be securely derived from this verse is that now that they are in the faith it is unfathomable that God would not finish what He started.

will perform it: This verb is the same one Jesus uses when He cries out "it is finished" from the cross in John 19:30. He will accomplish the purpose for which he began to do this good work in the Philippians. The wording here is at least reminiscent of God's promise to Israel in Jeremiah 29:10-11.

until the day of Jesus Christ: The phrases "until now" in verse 5 and "until the day of Jesus Christ" are parallel. Just as Paul gives thanks because the Philippians have been faithful in the gospel from the day they were saved until now (in verse 5), so he also gives thanks because God will be faithful to finish the gospel in the Philippians from the beginning of their salvation until the very end--that is, until Christ Himself returns. Eternal security is in no way dependent on the faithfulness of the Philippians. Quite to the contrary in this passage, Paul makes it clear that while the Philippians have been faithful, and he is grateful for their faithfulness, it is God's faithfulness that will finish the work, hence the same confidence toward a carnal and conflicted church in 1 Corinthians 1:8-9.

will perform it until the day of Jesus Christ: These two phrases together comprise the assurance that the security of the believer is both teleological (emphasizing the purpose of God) and eschatological (emphasizing the temporal accomplishment of that purpose).

Paraphrase:
I am grateful because of the persuasion that now holds me, a confidence that the One who began to work deliverance in you before you knew what He was doing will finish what He started and accomplish the purpose for which He began it, right up until the day Christ returns.