Sanctification is often an illusive idea for Christians, myself included. Too often people run to one extreme camp or the other. Some become legalistic, placing heavy burdens on the shoulders of Christians, over emphasizing rules, good habits, and being "holy". Other people stress grace and God's mercy rather than attempt to define any principles at all in fear of sounding legalistic. When this subject came up in my counseling class today, I immediately thought of Philippians 2:12-13
12 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, 13 for it is God who works in you, both to will and to work for his good pleasure.

When you first read this is sounds very strange. Work out my own salvation? What does that mean? I thought it was God who saves! A careful reading illuminates what sanctification looks like.

The first thing to note is that we are commanded to work out while God works in. This is helpful in that we are limited to an outer work. You can not sit down and change your own wicked heart, it is God who does that. In other words, God must work in for our salvation so what we can work out our salvation. Hence the word "for" squeezed in between the two. Paul is saying "work out your salvation because God is working in you". He is not saying, do this so God will work in you, he is saying do this because God works in you. Imagine, right before the word "for" the question "Why?".

The second thing to note is the different words Paul actually uses. The word he uses for "work" is a different word and aspect than the word for "works".

The word for work in the Greek is κατεργάζεσθε which means cause, perform, work out. It is a 2nd person plural present imperative which means Paul is using it as a command to the Philippians. He is essentially saying, "Hey, you all, do this."

The word for works in the Greek is ἐνεργῶν which means do, be effectual, be mighty in. It is a present active participle which means Paul is saying this is something God is continually doing.

Paul is not saying that we do some work outwardly and God does some work inwardly and it is a mutual effort from both parties like a three legged race where two people are tied together. The work being done by both parties is different in substance (one is outward one is inward) and different in aspect (one is commanded one is continual). So Paul is saying that we are to outwardly show what God is continually doing in us. Think about that for a minute. We are not outwardly working to be saved, we are outwardly working because we're saved. Remember that word "for" squeezed in between the two statements?

This setup is pivotal in never boasting because any outward work is based on the continual inward work that God is doing. Realizing that God is continually and inwardly working on us is the only way we will achieve the attitude that Paul prescribed: "with fear and trembling". Once you grasp this truth, that God is mightily and continually working inwardly on your heart, then you will fearfully and reverently attempt to work outwardly to show this. In fact, Paul uses the same word for the final "work" as he did when he said "works". This means we will do mighty and effectual things for God's good pleasure as an outpouring of the continual mighty and effectual work being done in us. Is there still a tension here? Yes. But this sheds light on the inter-workings of sanctification that hopefully fuels the fearful outworking of our salvation.