From what I understand of the belief of eternal security is that once one accepts Jesus Christ into their hearts and pray the ‘sinners’ prayer then there is no sin, no evil this individual can do so as to keep them from reaching heaven. They only need to believe in Jesus (John 3:16) and they’ll be ‘saved’. They have absolute assurance of salvation. And since works do not gain our salvation, our works cannot contribute to our losing our salvation. We are now “hid” with Christ in God (Colossians 3:3). There is “no condemnation” for those in Christ (Romans 8:1-2).
In fact some also bring up John 10:27 as proof that they can never lose their salvation since Jesus proclaims that “My sheep hear my voice, and I know them, and they follow me: And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand.” And yet nowhere do we find that one cannot willingly jump out of His hands through ones own choosing.
In fact, one Protestant writes:
“However, it is not merely from the Levitical laws that we were discharged, but also from the moral ones. God only has one law. Does that mean we can sin freely? No, for God hates sin, and if we love God, we will live according to His commandments. However, it does mean that no sin will be held against us once we receive Christ, for upon receiving Christ we are discharged from the very law against which our sins would have been reckoned.”
Let’s look at the question of absolute assurance. Is there such a teaching in Scripture? NO, there isn’t. Romans 8:1-2 does not say absolute assurance.
Rom 8:1-2 “Therefore, there is now no condemnation for those who are in Christ Jesus, because through Christ Jesus the law of the Spirit of life set me free from the law of sin and death.”
And Romans 6:15-16 says that sin leads to death. Now, this verse is found in the SAME letter as the verse supposedly showing absolute assurance. Decidedly, Paul does not agree with this. We are not discharged from the moral law because there are consequences to sinning!!
For example, what happens if a believer in Jesus cannot forgive the sins of another? Jesus Himself says that: “…if you forgive other people when they sin against you, your heavenly Father will also forgive you. But if you do not forgive others their sins, your Father will not forgive your sins.” (Mat 6:14-15)
God is infinite in His resources, He spares nothing to convince us to come to Him and remain BUT because of our free will, we are always free to refuse God's infinite help and support and in this way even lose our own salvation and therefore the Protestant doctrine of Eternal Security is unequivocally false.