"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." (Philippians 2:12)
We are not told here to work for our salvation, but to work it out—that is, to demonstrate its reality in our daily lives. Our salvation must be received entirely by grace through faith, not of works (Ephesians 2:8-9), or else it is not true salvation. Works can no more keep our salvation than they can earn it for us in the first place. It is not faith plus works, but grace through faith.
Nevertheless, a Christian believer, if his salvation has been real, can testify that "I will show thee my faith by my works" (James 2:18). Good works—consisting of a righteous and gracious lifestyle, considerate of others and obedient to Christ's commands—are the visible evidences of salvation. We have been "created in Christ Jesus unto good works, which God hath before ordained that we should walk in them" (Ephesians 2:10).
The context of our text, in fact, assures us, on the basis of Christ's sacrificial death, glorious resurrection, and exaltation (Philippians 2:8-11) that "it is God which worketh in you both to will and to do of his good pleasure" (v. 13). God is thereby enabling us to "work out" our salvation in visible practice, through the indwelling Holy Spirit of God.
Thus, it is beautifully appropriate that the life of a genuinely born-again Christian, possessing true salvation, should be "blameless and harmless, the sons of God, . . . as lights in the world; Holding forth the word of life . . ." (vv. 15-16). We do need to "examine |ourselves|, whether |we| be in the faith" (2 Corinthians 13:5), and we are admonished that "we do know that we know him, if we keep his commandments" (1 John 2:3). HMM