Two days ago we looked at the operation of grace, so this may seem a little bit of a contradiction but we are now looking at our response to God in light of the grace we have received. This is also from the book 101 Most Puzzling Bible Verses (Harvest House)
Keep on Keeping On
NIV Phil 2:12 Therefore, my dear friends, as you have always obeyed—not only in my presence, but now much more in my absence—continue to work out your salvation with fear and trembling
When Paul told the Philippians to work out their salvation, he did not mean they were to work for it or acquire it through their own efforts. In fact, they were already secure in their belief and salvation. (Phil 1:1) No one, ourselves included, can work for salvation because it is a gift from God (Eph 2:8-9). Salvation involves deliverance from the penalty and eternal consequences of sin, but every Christian is responsible for his or her own spiritual development and struggles with the daily consequences of the sin nature. While the Holy Spirit actively works in our lives, success or failure is up to us (Rom. 8:9,14,16).
Paul command the Philippians to put into practice through the aid of the Holy Spirit the results of the salvation they received from God. God would enable them to do it, (Phil 2:13) but they needed to actively pursue the ramifications of having eternal life and the benefits of living Godly lives. Spiritual progress is a cooperative effort between the Christian and the Holy Spirit. It is an outworking of a person’s rebirth as a Christian.
Paul was certain that just as God worked in his life and through him, so too would God work in the Philippians’ lives (Phil 1:6; 4:9). Because of this they were to be joyful in daily life (as should be all Christians), but they were also to understand the enormous responsibility and obligation of serving Jesus Christ. They were (and we are) to serve with “fear and trembling.” Being joyful and being fearful might seem to be contradictions, but they are not.
Paul uses the phrase “fear and trembling” several times to indicate a positive emotional response to understanding God’s desires for those He loves (I Cor 2:3; II Cor 7:15; Eph. 6:5). It is an attitude of obedience and awe rather than freight. To experience God’s best in our lives, we must have complete trust in Him and in the unique plan he has for each of us. As we journey with God, we work out our salvation, fully realizing the magnitude of the gift He has given us. In much the same way that the gift of luxury automobile is fully understood and appreciated only as the new owner drives it, so too is salvation more fully comprehended as a person daily lives according to God’s plan and God’s word. Fine automobiles are not meant to stay in the garage, and salvation is not meant to be dormant or static.
~ Tim Demy in 101 Most Puzzling Bible Verses, chapter 77