Most think once saved forever saved but that is where we get it wrong. Salvation is a daily activity and process to know more of and about God. One problem of the today christian is that we are mostly relaxed not until we find ourselves in problem
It is a good question, we should ask often
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The first thing to establish is, "what do we need salvation from"
Sin
Rom 6:23 For the wages of sin is death;
Death comes to all that sin.
Justice requires it. Sin is like a cancer and needs to be eliminated.
We are infected with sin.
Like a disease we are destined to die.
Eternal death...
Rom 6:23 .....
but the gift of God is eternal life through Jesus Christ our Lord.
Jesus gives us Eternal life as a gift.
Eph 2:8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
But how can God be just, (not break the law that sin =death) and gracious (give us forgiveness) at the same time.
The plan of salvation was that Jesus becomes a Man (second Adam) and defeats the devil, claims victory over sin and pays the price for sinning (death).
When our case is being judged we can stand before the judge fully covered in the righteousness of Jesus (perfection) or stand in our own righteousness. If we have one sin we will be lost.
We need to trust and believe and walk in Jesus.
Rom 8:1-2
There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit. 2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.