The term "Eternal Security" is nowhere to found in Scripture. The word "eternal" and the word "security" both occur in Scripture, but never together. Therefore, the term "Eternal Security" is clearly unbiblical.
Also observe that nowhere in Scripture is the idea of a Christian's security of salvation preceded with the qualifier of "eternal." If the bible doesn't use it, then why are people so insistent in putting the two terms together? Why would they insist on a qualifier when the Bible does not append one? And even more insulting to the Word of God... they insist that it is Biblical!
So why should we follow or believe that which has no foundation in the Bible? But... you say, "the concept is in the Bible, so it is OK."
One must inquire as to where they get such a "concept." If they are hanging all of their hopes on the word "eternal," then they will be hopelessly disappointed. They believe that the use of the term "life" with the preceding qualifier "eternal," settles the question forever. What they fail to recognize is what the Bible says. For the Bible states that this "life" is in God. For this "life" to be eternal, it must be connected to God who is eternal. The Bible states that believers have eternal life, but the Bible never states that anyone has an "eternal possession" of that life. You see, "eternal" is the quality of the life, not the quality to describe a person's possession of it. I can be given an eternal diamond that will never wear out or perish. As long as I posses and treasure it, it is mine. But if I no longer value it as I once did, or choose to trade it off for something else, it would mean that I no longer had personal possession of it any longer. But keep in mind, the diamonds quality didn't change in the least! It is still and "eternal" diamond that will never wear out or perish. Those that insist that they have an eternal possession of it must do the impossible, which is to show us the verse that states that we have this life as an irrevocable, eternal possession.
Is this concept in the Scriptures? Then where do the Scriptures say that "you cannot ever lose your salvation"? It seems strange that this doctrine which is so pivotal to most peoples idea of the Gospel doesn't have a single passage from Scripture that clearly states its meaning! You would think that if this doctrine was as important as people make it out to be, that the Bible would be chocked full of verses that stated this all so unambiguously. But we are reduced to the more unclear passages for "proof" of this concept. We must lower ourselves into reading Eternal Security into these passages in order to get Eternal Security out of them. I don't know about you, but I would rather get my doctrine from the Scriptures, not the other way around.
We are told that Eternal Security is all throughout the Scriptures. There are only about 12-15 verses that they can really appeal to, but upon a close examination, none of them ever state what they claim the doctrine of Eternal Security says. Now, with the idea that Eternal Security is true, even without a single Scripture to prove it, one can be easily deceived and mislead to read the doctrine into these passages which were never written to prove such a thing.
For these passages I will give the reader the link for their consideration.
The Eight Pillars of Eternal Security More Pillars of Eternal Security