This verse presents great comfort to the doubting Christian. The “good work” of salvation is presented as past, present, and future. Paul speaks of our salvation as a divine work of justification. It was not I who started this work; it was not my initiative or ability. God began the work for us, and therefore it is His work and His reputation that are at stake. Paul also speaks of our salvation as a developing work. This is our sanctification that He “will perform” in us and that we will evidence in our lives (see verse 7). But this is a definite work of salvation; its development is not tenuous—He will go on to complete it in our glorification at the day of Jesus Christ. Since our salvation is dependant on Christ, there is no chance of failure or incompletion. We can be confident of this very thing.
Reading: “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.”—Philippians 1:6