NET
6 For I am sure of this very thing, that the one who began a good work in you will perfect it until the day of Christ Jesus.
Darby
6 having confidence of this very thing, that he who has begun in you a good work will complete it unto Jesus Christ's day:
KJV
6 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: