“Can a saved person ever be lost? Can a Christian, a person who has received Jesus Christ as his personal Saviour, sin to such a degree that he will lose his salvation, go to hell or Hades at death, and eventually be consigned to the lake of fire at the great white throne judgment?” 
That question takes on clearer focus if we first answer two other questions: (1) What does it mean to be lost? (2) What does it mean to be saved?
What does it mean to be lost?
Jesus came to seek and to save those who are lost (Luke 19:10). What does it mean to be a lost and guilty sinner in the eyes of God? Why is it that the non-Christian is under the wrath of God? (John 3:36)
The essential reason that we all were once lost and guilty sinners under the wrath of God was our relationship to sin—any lack of conformity to the character and will of God.
Are we sinners because we sin, or do we sin because we are sinners? Both are true. The Bible says that we are all guilty of personal acts and attitudes of sin (Romans 3:23; cf. 3:10-18; Mark. 7:20-23). It also indicates that we are guilty because we are born with a sinful nature (Psalm 51:5), ultimately inherited from our ancestral father, Adam. The Bible even shows that all humankind is viewed by God as having sinned in Adam's initial sin (Romans 5:12).
The penalty that is the result of our sin is death…
Scripture describes our condition before believing in Jesus Christ as being under the wrath of God:
What does it mean to be saved?
“Salvation is from the LORD” (Jonah 2:9). It is both negative and positive (Colossians 1:13), for we are saved from a lost condition (our sins are forgiven), and we are brought into a saved condition that provides the believer with several dozen positive blessings the moment we trust Christ.
These blessings are very comprehensive, for our "salvation includes every divine undertaking for the believer from his deliverance out of the lost estate to his final presentation in glory conformed to the image of Christ."  Paul declares that God has already blessed us with all spiritual blessings in Christ (Ephesians 1:3).
Some of the principal blessings of salvation include:
Can a saved person ever again be lost?
Can a Christian lose his salvation? Can a person once saved, having received God's free gift of eternal life and having been born into the family of God, again return exactly and completely to the position of being a lost and guilty sinner in the eyes of God? Of course not! The very nature of the spiritual life that has been received—eternal—and the Divine Source and Agent of that life—God—forbid drawing the conclusion that a saved person can ever again be lost.
This Biblical doctrine that a person who has received Jesus Christ, been born into the family of God, and justified by faith, can never again be lost is sometimes called eternal security. Others speak of it as the perseverance of the saints. The latter expression might better be termed the perseverance of God in behalf of the saints, because the security of our salvation does not rest on us but on God—it is based on the work of the Father, the Son, and the Holy Spirit.
What is the work of the Father in securing eternally our salvation?
The eternal security of believers rests on the Father's purpose in choosing us to salvation in eternity past and predestinating us to sonship in Jesus Christ (Ephesians 1:4-5).
Further, God's power is promised to keep us secure in salvation (Romans 8:28-30), for the ones that the Father foreknew, predestined, called (effectually to salvation, cf. 1 Corinthians 1:21-24), and justified are the very same ones he “glorified”. (Paul uses the past tense since in God's sight it is “good as done” that we will one day be conformed to the image of Christ in heaven).
Further, Jesus Christ guaranteed that we are secure in His and the Father's hand, and so He will keep safe each one who has received the gift of eternal life (John 10:28-29).
What is the work of the Son in securing eternally our salvation?
Our security further rests on the death and the prayers of Jesus Christ. He has redeemed us (Ephesians 1:7) and removed the wrath of God from us (Romans 3:25) so that we may be justified (Romans 5:1), forgiven (Colossians 2:13), and sanctified (1 Corinthians 1:2).
What is the work of the Holy Spirit in securing eternally our salvation?
By the regenerating work of the Holy Spirit, we have received eternal life (Titus 3:5). When we trusted Christ, the Holy Spirit began an eternal indwelling ministry in us (John 14:17). Also He was the seal placed on us by the Father to guarantee our future inheritance (Ephesians 4:30). And He baptized us into union with Christ and into the body of believers (1 Corinthians 12:13).
Can a saved person ever be lost?
MORE INFORMATION ON SALVATION and related topics
Author: Dr. Duane Lindsey.
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