Since Romans 10:9 has been thrown around a lot on this thread (and I admit there are portions of the thread that I really just skimmed or skipped over), I wanted to point something out :
But what saith it? The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach;
That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.
Romans 10:8-9
The first point is that we already have a command : Confess.
But the second point is that Paul goes on to explain what precedes that salvation :
For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.
For the scripture saith, Whosoever believeth on him shall not be ashamed.
For there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him.
For whosoever shall call upon the name of the Lord shall be saved.
How then shall they call on him in whom they have not believed? and how shall they believe in him of whom they have not heard? and how shall they hear without a preacher?
And how shall they preach, except they be sent? as it is written, How beautiful are the feet of them that preach the gospel of peace, and bring glad tidings of good things!
Romans 10:10-15
Paul makes the point that that confession is loaded with faith and that faith comes from hearing the Word preached. And in that second passage is buried verse 13. That whosoever calls upon the name of the Lord shall be saved. We hear the name of the Lord used in many contexts every day. But who actually calls on the name of the Lord? One who believes. And who believes? One whose heart has been changed by God. One may well say they believe, but the calling upon the Lord comes only from a heart that believes that He saves. The analogy I think works best is the one who says they believe in a parachute but won't put it on. They either don't believe they need it or they don't believe it will work. But if they do put it on, they are actively trusting in it. Is that a work? It is, but is it that faith in the parachute which actively saves? No. It's the parachute that does all the saving work. All you do is trust the parachute enough to put it on and jump. That's the parallel to confessing Christ. Is that a work? Maybe. And it is absolutely essential to salvation. But does it save? Absolutely not. If it did, that would be salvation by works.
EDIT : My opinion is the instaneous view of salvation has done understanding of this a great disservice. As soon as you call salvation something that happens in a moment and emphasize that over the evidence of a lifetime walk, you get these debates that are endless - debates over words that ignore the fruit of a whole life in favor of the power found in a single moment. The moment of salvation is often spectacular, but it is only the beginning.