Once saved, always saved is at the very heart of Christianity
The doctrine of eternal security is at the very heart of the Christian faith. Once you take away the doctrine of Once saved, always saved, you cease to believe in Christianity and you believe something else.
The doctrine of eternal security has its foundations in those doctrines that are central to the Christian faith:
In Christ, humanity and deity are joined together in perfect union. Those who are in Christ are united to the Godhead. Humanity is joined to deity and men and women can live the divine life, eternal life, enjoying the eternal existence of God.
The Substitutionary death of our Lord
The death of Christ frees the believer from death. Eternal redemption has been secured through the sacrificial death of the Lord Jesus Christ.
The Resurrection of our Lord
The believer is justified in the risen Christ. She is dead and risen with Him. Just as Christ can never die again, the believer can never perish.
The Ascension of our Lord
The Lord Jesus has ascended into heaven where He is our representative. Through their union with Him, the believers' place and privilege is in heaven. That is where the believer eternally belongs.
The New Birth
The believer is beome a child of God. Just as a child can never cease to be the son or daughter of her parents, the believer can never cease to be a child of God.
The Indwelling of the Holy Spirit
The believer is indwellt with the Holy Spirit. The Scriptures say nothing about the Holy Spirit ceasing to indwell a Christian.
The believer is brough into the church which is the body of Christ. That body is an indivisible union, not a voluntary association.
The discipline and judgment of the believer
Though it be a fearful thing, the Father's discipline and chastening of believers reveals His fatherly care and ownership of the child of God.
The Resurrection and Glorification of the Elect
Those who are called and justified are to be raised from the dead and glorified. "We shall not all sleep, but we shall be changed." "So shall we ever be with the Lord."
The New Heavens and the New Earth
The regeneration of the believer is a type and foretaste of the renewal of the cosmos. Just as the restoration of creation is a certain fact, so is the believer;s eternal security.