Being confident of this, that he who began a good work in you will carry it on to completion until the day of Christ Jesus. (NIV)
As Paul begins his letter to the Philippian church (Phil. 1:1-6), he expresses his thanks to God for how good he felt toward them—indeed for how confident he was that their salvation was secure in Christ, and that it would be secure until “the day of Jesus Christ.” That day will be the day of the rapture, which will be the first phase of His coming.
This introduction (vv. 1-6) is very similar to Paul’s introduction to the Corinthian church (1 Cor. 1:4-7), in that he expresses his confidence that they would be found blameless when He comes, hence, that God’s good work of grace would continue until He comes.
What a wonderful truth this is—that though we sin every day, His wonderful work of grace forgives us (those who believe) and keeps us blameless until we see Him face to face.