Romans 10:9-10I might think that I will be saved immediately if I confess on my lips and believe in my heart; this is the doctrine found in some protestant denominations. I might also believe that when the condition is met once, it lasts forever, which is the once-saved, always-saved doctrine, also found in some protestant denominations. I could even think that eventually, enough belief and confession will earn me salvation, this is a merit-based salvation doctrine that many Christians fall into but that no denominations officially teach to my knowledge. But in order to understand the intended meaning of this particular verse, we should look deeper at what the term "be saved" means, and look to other verses to help us discern. The second sentence gives us a little clue, in that it separates being saved into multiple aspects. To understand the different aspects of salvation, we must ask the question "what are we being saved from?" The simplest result of salvation is that we're saved from the consequences of sin, the eternal separation from God; this is justification. But another result of salvation is that we are also being saved from sin itself, through a gradual process, being healed to the point where we eventually commit no sins and fully love God. This is the part of salvation called sanctification.
For if you confess on your lips that Jesus is Lord, and believe in your hearts that God raised him from the dead, you will be saved. Faith in the heart leads to justification, confession on the lips to salvation.
Philippians 2:12 Therefore, my dear friends, as you have always obeyed—not only in my presence, but now much more in my absence—continue to work out your salvation with fear and trembling
2 Thessalonians 2:13
But we ought always to thank God for you, brothers and sisters loved by the Lord, because God chose you as firstfruits to be saved through the sanctifying work of the Spirit and through belief in the truth.
2 Timothy 1:9
He has saved us and called us to a holy life—not because of anything we have done but because of his own purpose and grace. This grace was given us in Christ Jesus before the beginning of time
But when the kindness and love of God our Savior appeared, he saved us, not because of righteous things we had done, but because of his mercy. He saved us through the washing of rebirth and renewal by the Holy Spirit, whom he poured out on us generously through Jesus Christ our Savior, so that, having been justified by his grace, we might become heirs having the hope of eternal life.
John 15:2-7These imply that salvation needs to be worked out, that it is an on-going process, that it isn't an instantaneous result of a single prayer, that it isn't guaranteed, that the condition "if you remain in me" is an on-going condition.
I am the true vine, and my Father is the gardener. He cuts off every branch in me that bears no fruit, while every branch that does bear fruit he prunes so that it will be even more fruitful. You are already clean because of the word I have spoken to you. Remain in me, as I also remain in you. No branch can bear fruit by itself; it must remain in the vine. Neither can you bear fruit unless you remain in me. “I am the vine; you are the branches. If you remain in me and I in you, you will bear much fruit; apart from me you can do nothing. If you do not remain in me, you are like a branch that is thrown away and withers; such branches are picked up, thrown into the fire and burned. If you remain in me and my words remain in you, ask whatever you wish, and it will be done for you."
Looking at it this way, salvation is a three-part entity, a state of being (justification), a process (sanctification), and an end goal (eternity with God, free from sin),