We need all the parts of Paul’s statement in Philippians 2:12-13.
Therefore, my beloved, as you have always obeyed, so now, not only as in my presence but much more in my absence, work out your own salvation with fear and trembling, for it is God who works in you, both to will and to work for his good pleasure. (Philippians 2:12–13, ESV)
Certainly, Paul is encouraging us to a life of obedience, individual responsibility, and perseverance. But we need to notice more than the phrase: work out your own salvation.
Paul wants us to live a life of reverence. Interestingly enough, Paul emphasizes “with fear and trembling” by his word order. Literally in Greek, the phrase would be: with fear and trembling your own salvation work out. That provides a context for our obedience. We are in a relationship with a mighty God.
Certainly a terror that would cause us to freeze or flee would be counter-productive. But the fear or reverence that Paul wants us to have should cause us to be humble and receptive. “The fear of the Lord is the beginning of knowledge; fools despise wisdom and instruction” (Proverbs 1:7, ESV). “But this is the one to whom I will look: he who is humble and contrite in spirit and trembles at my word” (Isaiah 66:2b, ESV).
Paul wants us to live a life of power. That is why reverence is so important. We are living in a relationship with God — a life of dependence. Paul explains that in this working out of our own salvation that God is involved: “for it is God who works in you, both to will and to work for his good pleasure” (Philippians 2:13, ESV). My experience in Christian living would suggest that God’s power doesn’t help us without our effort and cooperation. I think that is why there is the balance that exists in this passage. But neither should we think that the walk of faith is unaided and dependent only on our own resources.
Paul is clear that he has a source of strength that is beyond himself: “I can do all things through him who strengthens me” (Philippians 4:13, ESV). I suspect we discover God’s power in our lives when we admit our own weaknesses in prayer. I suspect we find God’s help when we step out in faith despite our own reservations.
Paul clearly wants us to understand our part and God’s part in daily Christian living. Work out your own salvation. But remember we do this in fear and trembling, and that God is at work in us to will and to work for his good pleasure.