Once Saved Always Saved?

When John Calvin organized the many beliefs that are now referred to the TULIP doctrine, he included as the last point, “Perseverance of the saints.” This says that once man is saved, he cannot be lost. It is commonly referred to as “once saved, always saved.”  They say that it is impossible to fall from God’s grace regardless of what you do.  This may sound good and comforting, but what does the Bible say?  In 1 Corinthians 9:27 the apostle Paul says, “but I discipline my body and make it my slave, so that, after I have preached to others, I myself will not be disqualified.”  Paul understood it was possible for him to become disqualified.  Webster’s dictionary defines disqualified as, “to stop or prevent (someone) from doing, having, or being a part of something.” If Paul became disqualified he would be lost.
In 1 Corinthians 10:12 Paul gives a warning to the Christians at Corinth by saying, “Therefore let him who thinks he stands take heed that he does not fall.”  Why would this warning be necessary if it is impossible to fall?  So, the very people, who think they cannot fall, are given a warning to take heed lest they fall.
In Galatians 5:4 we read, “You have been severed from Christ, you who are seeking to be justified by law; you have fallen from grace.”  Doesn’t it seem strange, that people who say they believe the Bible also say that we cannot fall from grace, when the Bible so plainly says that we can fall from grace.  Who are we to believe, God or man?  Even though many religious bodies say that you cannot fall from grace, the Bible clearly says that people can fall from grace.  And without God’s grace we cannot be saved.
The doctrine of “once saved always saved” and that you cannot fall from God’s grace and be lost is a doctrine that did not come from God but rather originated with Satan.  Satan wants people to believe that they cannot fall from grace and be lost to entice them into doing wrong.  In Genesis 2:17 God told Adam and Eve, “…from the tree of the knowledge of good and evil you shall not eat, for in the day that you eat from it you will surely die.”  But in Genesis 3:4 Satan told Eve, “You surely will not die.”  Satan only added the word “not” to what God had said.  Just as Satan told a lie to Eve, Satan is still deceiving people today by telling them they cannot fall from grace and once they are saved, they are always saved.  He is trying to lull people into complacency.  This is one of the many ways that Satan deceives people so they will be eternally lost.  But 2 Peter 1:10 says, “be all the more diligent to make certain about His calling and choosing you.”
God’s promises are conditional upon our doing His will.  Jesus says in Matthew 7:21, “Not everyone who says to Me, ‘Lord, Lord,’ will enter the kingdom of heaven, but he who does the will of My Father who is in heaven will enter.”  Also, Hebrews 5:9 says concerning Jesus that “He became to all those who obey Him the source of eternal salvation.”
Note: All scriptures are quoted from the New American Standard Version Updated 1995