One of the basic doctrines of Calvinism is the impossibility of apostasy. This teaching says that once a person becomes a Christian there is nothing he or she can do to be lost One man went so far as to say that even if he murdered someone in cold blood he could not be lost.
This is not the kind of security that is taught in the Bible. For the Christian, eternal life is based on faithfulness throughout life. Peter said to those who add the “Christian Graces”: “For if you do these things you will never stumble” (2 Peter 1:10). This is a conditional statement. Never stumbling is dependent upon doing what God requires. However, there is security in that promise. Other statements are equally reassuring.
John makes it clear that those who keep loving others are assured of life. “We know that we have passed from death to life, because we love the brethren. He who does not love his brother abides in death” (1 John 3:14). Again John wrote: “The world is passing away, and the lust of it; but he who does the will of God abides forever” (1 John 2:17), All but the most casual reader will be impressed with the fact that those who practice obedience to God’s will have complete assurance of eternal life.
One other Scripture citation will be given from the apostle John, “but if we walk in the light as He is in the light, we have fellowship with one another, and the blood of Jesus Christ His Son cleanses us from all sin” (1 John 1:7).
Fellowship is possible where there is agreement. Agreement with God is indicated by the statement “walk in the light.” Thus, those who walk in the light of God’s will have continual fellowship with God, This is security!
via Nettleton church of Christ