God wants us to choose Him and use our free will to choose His Will, but even though He knows some will depart from the faith, He still honors our free will and leaves these choices up to us.....
"The Lord is with you while you are with Him. If you seek Him, He will be found by you; but if you forsake Him, He will forsake you." (2Chronicles 15:2b)
“As for you, my son Solomon, know the God of your father, and serve Him with a loyal heart and with a willing mind; for the Lord searches all hearts and understands all the intent of the thoughts. If you seek Him, He will be found by you; but if you forsake Him, He will cast you off forever." (1Chronicles 28:9)
Some may find these Scriptures antagonistic to the Once Saved Always Saved 'doctrine;' that's because they are, in fact, they prove positively that to call that Promise of God a doctrine is incorrect and unbiblical.
It's certainly and wonderfully true; an indisputable fact that God will never leave nor forsake His children, however, anyone having the ability to turn on God was never His child in the first place.
This is a pure and simple concept; we were given free will, God did not program us, therefore, how can we believe that He would refuse to let those wanting out of what He has to offer deliberately opt out of the faith?
How can we believe that He would refuse to allow those who choose to, to opt out of following Him? If it's our choice, then we do not at any point, lose the ability to choose and that includes the changing of one's mind. God says this very thing to the Israelites in Deuteronomy 30:15-20--
“See, I have set before you today life and good, death and evil, in that I command you today to love the Lord your God, to walk in His ways, and to keep His commandments, His statutes, and His judgments, that you may live and multiply; and the Lord your God will bless you in the land which you go to possess. But if your heart turns away so that you do not hear, and are drawn away, and worship other gods and serve them, I announce to you today that you shall surely perish; you shall not prolong your days in the land which you cross over the Jordan to go in and possess. I call heaven and earth as witnesses today against you, that I have set before you life and death, blessing and cursing; therefore choose life, that both you and your descendants may live; that you may love the Lord your God, that you may obey His voice, and that you may cling to Him, for He is your life and the length of your days; and that you may dwell in the land which the Lord swore to your fathers, to Abraham, Isaac, and Jacob, to give them.”
But God is faithful to His children.......
"For He Himself has said, “I will never leave you nor forsake you.” So we may boldly say:
“The Lord is my helper;I will not fear.What can man do to me?” "(Hebrews 13:5b-6)
So the conclusion we can draw in regard to the Once Saved Always Saved 'doctrine' is that is not a doctrine at all, but a promise from our God to never leave us nor forsake us, but that doesn't mean we are stripped of the freedom to forsake Him. We have that right at all times.
In Christ we are free:
"Even so we, when we were children, were in bondage under the elements of the world: But when the fulness of the time was come, God sent forth his Son, made of a woman, made under the law, To redeem them that were under the law, that we might receive the adoption of sons. And because ye are sons, God hath sent forth the Spirit of his Son into your hearts, crying, Abba, Father. Wherefore thou art no more a servant, but a son; and if a son, then an heir of God through Christ." (Galatians 4:3-7)
No matter how hard it may be to imagine, there are those who do make the unfathomable choice to turn away from the faith and their Creator.
The real danger of the OSAS 'doctrine' is that those who hold to this teaching may not even realize that if they consciously turn away from God, even if they see it as temporary (scheduling sin/repentance, which is unacceptable to God); God counts it as betrayal.....
God will never forsake His children, but those who think they can forsake Him, and He just looks the other way, are misled and have taken God's Promise of Supreme Loyalty out of context.
"Do not be deceived, God is not mocked; for whatever a man sows, that he will also reap. For he who sows to his flesh will of the flesh reap corruption, but he who sows to the Spirit will of the Spirit reap everlasting life." (Galatians 6:1-8)