Eternal security in 3 points - Full Assurance of Salvation

Eternal security – How to know you are saved.

But the gift of God (1) is eternal life (2) through Jesus Christ our Lord (3). - Romans 6:23b - And this is the record, that God hath given to us (1) eternal life (2), and this life is in his Son (3). - 1John 5:11

1 - Salvation is a gift. You cannot earn it through any amount of works. Romans 4:5 says - But to him that worketh not (to earn salvation), but believeth on him (Jesus) that justifieth the ungodly, his faith is counted for righteousness. Salvation is freely given by God’s grace (by His unmerited favour), and must be freely received by faith (Eph. 2:8-9). If you could go to heaven on your own apart from Jesus, you would never make it because you'd have to be a 100% perfect and only do good all the time like Jesus Christ (from the beginning to the end of your life - without a single sin). And of course we know that's impossible because, truth be told, we all have sinned, and for honest persons, we still and always will sin as long as we are in this carnal, corrupt body (1John 1:8) - either by will or by ignorance. We all need to be saved.

2 - Salvation is eternal. It will last forever and you can never lose it once you've received it. It is based on God's promise, and not on your own faithfulness to keep God’s commandments, etc. ‘’In hope of eternal life, which God, that cannot lie, promised before the world began (Titus 1:2)’’.  In order to be saved, a person must believe that God gives eternal life as a free gift based on Jesus’ payment for our sins, and not temporary life (conditional salvation) based on human efforts or works (which would make salvation a reward instead of a gift) - Jesus' sacrifice gives ''eternal redemption'' (Heb. 9:12) and eternal life to the believer who completely rests in Him apart from works. Hebrews 4:9-11 reads - There remaineth therefore a rest to the people of God (i.e. all saved Christians). For he that is entered into his rest (God's rest - eternal life, or salvation), he also hath ceased from his own works (i.e. works of righteousness), as God did from his. Let us labour therefore to enter into that rest, lest any man fall after the same example of unbelief. (People who do not believe that salvation is eternal and free are calling God a liar and are not saved - they are trusting in their own works instead of trusting and believing God's record) - He that believeth on the Son of God hath the witness in himself: he that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son (1John 5:10). The record being that eternal is a gift that you receive once and for all through simple faith in Christ (the moment you believe the gospel – His death, burial and resurrection as the full payment for your sins), and that cannot ever lose salvation for any reason. God gave us (past tense) eternal life the moment we trusted Christ alone apart from all else (Jesus says in John 6:47- ... He that believeth on me hath (present tense) everlasting life)!

3 - Salvation is only through Jesus's death, burial and resurrection. But thankfully, God paid for our salvation in full with the death, burial and resurrection of Christ and promises eternal life to ''whoever believes'' and not ''whoever is good enough''. Salvation cannot be obtained through any other means than receiving Jesus's death on the cross, His burial and bodily resurrection - it is the only valid payment for man’s sins and the only means of receiving eternal life. The moment a person receives Christ as Saviour, their sins are put on Christ's account and the person receives Christ's righteousness (they are declared righteous before God because of Jesus' finished work alone - and not because of their own doing). They are justified from all things (Acts 13:39) (all their sins (past, present and future) are washed away forever through faith in His blood (Romans 3:25, Revelation 1:5) and they can no longer go to hell because they are saved forever (John 5:24). This is the way salvation (or eternal security) works. There is no salvation without unconditional eternal security!