"...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 2:13, NKJV)
This is a great scripture and very simple to explain. It is full of the grace of God and yet people have turned it into a very legalistic scripture to scare Christians into action in fear of losing their salvation if they don't.
The first thing to note is that is doesn't say "work for your salvation" it says "work out your salvation.” That is a big difference! A lot of people have completely changed this verse to mean work for your salvation or work to keep your salvation. And to do this with such fear and trembling because you just don't know if you might lose it and go to hell! Well excuse me, but who gave you the authority to change Scripture and abuse the Gospel and God's people? The verse says work out your salvation not work for your salvation. It is simply teaching us how to walk in the Spirit in this life. That it is God who works in us, and we respond by working it out in our lives. God puts things in us and it's us who then works them out in our lives by trusting in God and not in our flesh.
That is what the fear and trembling is talking about. "Fear and trembling" is not a phrase that is meant to strike fear in people's hearts and insecurity. In the New Testament whenever you see the phrase "fear and trembling,” it is only associated with good things! It is associated with an awe and respect for God with a sense of submission to His greatness. Its a trust in God and a distrust in our flesh. When Paul preached in Corinth, he said did so with much fear and trembling so that his confidence wouldn't be in his preaching but in the power of God! His fear and trembling was all about not having confidence in his flesh, but to put his confidence in God (1 Cor 2).
In Mark 5:33 the woman with the issue of blood also had fear and trembling, but it wasn't because Jesus had called her out and that she was scared of the consequences for being an "unclean woman among Jewish men.” Her fear and trembling was because she knew what had happened to her body, that she had been healed! It was an amazement and an awe of God at his mighty working in her body!
"But the woman, fearing and trembling, knowing what had happened to her, came and fell down before Him and told Him the whole truth.” (Mark 5:33, NKJV)
Now people who say that we must work for our salvation with fear and trembling seem to forget or leave out the part where it says, "...for it is God who works in you, both to will and to work for his good pleasure." People who do this end up actually teaching the very opposite of what this verse is teaching. They end up getting people in the flesh trying to work for their salvation when in actual fact this verse is trying to teach us how to walk in the Spirit and respond to God's working in us so that it can be gloriously worked out through our lives!
It is God who works in us. We then work it out through our lives! God works in and we work it out! God puts his goodness in us and we work it out through our lives. God puts his grace and his power in us and we work it out. God's puts his victory and strength in us and we work it out. God puts his wisdom in us and we work it out. God puts his Kingdom inside of us and we work it out through our lives. What a glorious picture of partnering with God. Oh and the way we work it out is simply to yield to him because it's God who works in us to will and do!
So to paraphrase this Scripture:
”...work out, through your lives, all the wonderful things that God has put in you. Trust in Him and put your confidence in him, not in yourself. He knows the plans and purposes that He has for your life and he is moving in you to give you the desire and the ability to walk in them! Simply yield and respond to God and He will ensure you live a powerful, spiritual and effective life in Him!”