We are given in Scripture many proofs of the eternal life promised in Christ for those who trust Him by Faith. Eternal life (rather than intermittent life), is one of the most clearly taught truths in scripture, and brings out the gospel (good tidings) of peace (as opposed to frustration, concern, uncertainty) in a way that shows the good will of God towards man. Knowing first that scriptures cannot contradict one another, since they are given by the Holy spirit, we can clearly determine the truth of this doctrine using the scripture in a way that brings peace to the soul rather than angst.
Firstly, all the transactional words used to describe the new birth of one who comes to Christ by the Spirit in faith are evidence themselves. Additionally, the only requirement for eternal life is to believe in Jesus Christ by Faith. Typically, eternal security comes under fire from those who are concerned that people will not “behave” if salvation isn’t contingent on our behavior in some way. But isn’t our behavior what got us into this mess to begin with? Certainly, it is not sufficient to get us out. Nor can we do “good works” that maintain salvation, since the righteousness necessary to be saved must be equal to God’s righteousness. That pretty well counts out our efforts at good behavior. Consider…
Justified – declared righteous and presented without guilt in a legal sense. If we have been justified by Christ and yet still waiting to be presented to God, we can know that He is able to keep that which we have committed unto Him against that day. (i.e. our whole spirit, soul, and body against the day of judgement - 1 Thessalonians 5:23)
Redeemed – bought and paid for and taken to God as a possession. Taken off the market when the Father redeemed us to Himself having been purchased by the blood of Christ. The blood of Christ being of infinite value, the Father will never sell us away, nor are we available, nor can a greater price be paid for us.
Adopted – Legally transacted into the permanent family of God as a son and joint heir with Christ.
Regenerated – Given the nature of a son of God having been adopted by the power of God through the blood of Christ and indwelt by the Holy Spirit
Saved – protected from the penalty of sin through the sacrifice of Christ Jesus and given sanctuary from the wrath of God against sinners.
The earnest of our inheritance – the term “earnest” is a legal term used to describe the down payment that we received from God before the full inheritance is received. It is a sign of the surety of His promises to those who believe.
This faith in Christ is more than A head knowledge that grips us As we listen to the words of a captivating speaker, just to drop us flat a short time later. The conviction that’s formed deep within our heart is the understanding that Jesus is not just a man. He is the Lord Himself, and that He willingly and lovingly took upon Himself the penalty for our sins, which is death. As proof that God counted His death as sufficient for sin, He raised Jesus from the dead to be seated at His right hand in Heavenly realms (Ephesians 1:20). For us to dwell in the presence of God every one of our sins has to have been paid for. This is what Christ has done when He gave Himself a sacrifice once for all (Hebrews 10:10).
Many other proofs are given in the scriptures themselves such as the fact that we are told when the Spirit comes to indwell a believer He abides forever (John 14:16) and that the Father is greater than all and no man is able to pluck us out of His hand (John 10:29). Believing the Gospel requires faith in what Christ has done in order to be saved, and any "faith" that requires us to keep ourselves saved proves we are still trusting ourselves rather than God.
remember there is also a great difference between the gift of salvation and the prize Paul speaks of that we should run to obtain. Gifts are for free, but prizes and rewards take hard work! That work must be built upon our faith, or it is of no value. Only works done in faith are acceptable in the sight of Christ.