Many Christians read this verse and then they may quote Eph. 2:8-9, saying “I thought we were saved by grace through faith alone.”

⁸ For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: ⁹ Not of works, lest any man should boast. Ephesians 2:8-9 (KJV)

So, what is the meaning of Paul’s words “work out your own salvation with fear and trembling” as seen here in Philippians 2:12? As you will see, ‘context’ matters and answers the question.

¹² Wherefore, my beloved, as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling. ¹³ For it is God which worketh In You both to will and to do of his good pleasure. Philippians 2:12-13 (KJV)

The context as seen in Philippians 2:12-13 continues the purpose for which Paul wrote to the Philippian saints as set forth here.

⁹ And this I pray, that your love may abound yet more and more in knowledge and in all judgment; ¹⁰ That ye may approve [prove out] things that are excellent; that ye may be sincere and without offence till the day of Christ; ¹¹ Being filled with the fruits of righteousness, which are by [of] Jesus Christ [in you], unto the glory and praise of God. Philippians 1:9-11 (KJV)

While the Philippian Church is a model church there are always seeds of dispute and room for improvement so Paul prays and writes to them concerning those things.  He concludes by saying: “Being filled [inwardly] with the fruits of righteousness, which are by Jesus Christ, unto the glory and praise of God.”

These kinds of “fruits” comes from the life of Christ within each believer.  Fruit is not the external, artificial works of the flesh, but of the life of the indwelling “Spirit of life in Christ Jesus.:  So, in encouraging the Philippians to “work out your own salvation” in Philippians 2:12-13, Paul is encouraging the Saints to work out that which is within.  They already had Salvation from perdition and they had God working in them (v13).  Now they are to out-work out that which is already within them.  Thus, Paul also wrote in 1Timothy 4:7 saying “exercise thyself rather unto godliness.”  So, the “salvation” in v12 is not salvation from the penalty of sin, but rather from the power of “sin in the flesh” of all men, saved and unsaved.” 

Here we see how that Paul worked out his salvation in thinking through his situation In Phil. 1:12-13, 19-21. 

¹² But I would ye should understand, brethren, that the things which happened unto me [in his imprisonment] have fallen out rather unto the furtherance of the gospel; ¹³ So that my bonds in Christ are manifest in all the palace [guard], and in all other places; Philippians 1:12-13 (KJV)

¹⁹ For I know that this shall turn to my salvation through your prayer, and the [inner] supply of the Spirit of Jesus Christ, ²⁰ According to my earnest expectation and my hope, that in nothing I shall be ashamed, but that with all boldness, as always, so now also Christ shall be magnified [seen] in my body, whether it be by life, or by death. ²¹ For to me to live is Christ, and to die is gain. Philippians 1:19-21 (KJV)

Paul then wrote of the Lord Jesus who always had the right mindset in his situations –at the Cross. 

⁵ Let this mind [Grk. phroneo, mindset] be in you, which was also in Christ Jesus: ⁶ Who, being in the form of God, thought it not robbery to be equal with God: ⁷ But made himself of no reputation, and took upon him the form of a servant, and was made in the likeness of men: ⁸ And being found in fashion as a man, he humbled himself, and became obedient unto death, even [that is] the death of the cross. Philippians 2:5-8 (KJV)

Now the Philippians saints are to have that same mind, i.e.; To live in anticipation of “the Day of Christ” – Philippians 1:6,10; 2:16. The “fear and trembling” of 2:12 is in light of ‘the Judgement Seat of Christ’ where we will give account of ourselves, of our service. Essentially, the question will be this: ‘What did we do with the life and power that God gave us when we were first saved?’

Paul’s prayer in Philippians 1:9-11 is the key. 

⁹ And this I pray, that your love may abound yet more and more in knowledge and in all judgment; ¹⁰ That ye may approve [prove out] things that are excellent; that ye may be sincere and without offence till the day of Christ; ¹¹ Being filled with the fruits of righteousness, which are by Jesus Christ, unto the glory and praise of God. Philippians 1:9-11 (KJV)