Eternal security is also conditional: All believers have full assurance of salvation with the condition that they remain in Christ. Salvation is conditioned on faith, therefore perseverance is also conditioned. Apostasy (turning from Christ) is only committed through a deliberate, willful rejection of Jesus and renouncement of belief.
John 15:5-6 - I [Jesus] am the vine, you [the disciples] are the branches. He who abides in Me, and I in him, bears much fruit; for without Me you can do nothing. If anyone does not abide in Me, he is cast out as a branch and is withered; and they gather them and throw them into the fire, and they are burned.
Gal 5:4 - You have become estranged from Christ, you who attempt to be justified by law; you have fallen from grace.
1 Tim 4:1-2 - Now the Spirit expressly says that in latter times some will depart from the faith, giving heed to deceiving spirits and doctrines of demons, speaking lies in hypocrisy, having their own conscience seared with a hot iron.
Heb 3:6b, 12-14 - [And we are His house] if we hold fast the confidence and the rejoicing of the hope firm to the end… Beware, brethren, lest there be in any of you an evil heart of unbelief in departing from the living God; but exhort one another daily, while it is called “Today,” lest any of you be hardened through the deceitfulness of sin. For we have become partakers of Christ if we hold the beginning of our confidence steadfast to the end.
Heb 6:4-6 - For it is impossible for those who were once enlightened, and have tasted the heavenly gift, and have become partakers of the Holy Spirit, and have tasted the good word of God and the powers of the age to come, if they fall away, to renew them again to repentance, since they crucify again for themselves the Son of God, and put Him to an open shame.
Heb 10:26-29 - For if we sin willfully after we have received the knowledge of the truth, there no longer remains a sacrifice for sins, but a certain fearful expectation of judgment, and fiery indignation which will devour the adversaries. Anyone who has rejected Moses’ law dies without mercy on the testimony of two or three witnesses. Of how much worse punishment, do you suppose, will he be thought worthy who has trampled the Son of God underfoot, counted the blood of the covenant by which he was sanctified a common thing, and insulted the Spirit of grace?
Heb 10:23, 35-36, 38-39 - Let us hold fast the confession of our hope without wavering, for He who promised is faithful… Therefore do not cast away your confidence, which has great reward. For you have need of endurance, so that after you have done the will of God, you may receive the promise…“Now the just shall live by faith; But if anyone draws back, My soul has no pleasure in him.” But we are not of those who draw back to perdition, but of those who believe to the saving of the soul.
James 5:19-20 - Brethren, if anyone among you wanders from the truth, and someone turns him back, let him know that he who turns a sinner from the error of his way will save a soul from death and cover a multitude of sins.
2 Peter 2:20-22 - For if, after they have escaped the pollutions of the world through the knowledge of the Lord and Savior Jesus Christ, they are again entangled in them and overcome, the latter end is worse for them than the beginning. For it would have been better for them not to have known the way of righteousness, than having known it, to turn from the holy commandment delivered to them. But it has happened to them according to the true proverb: “A dog returns to his own vomit,” and, "a sow, having washed, to her wallowing in the mire."
2 Peter 3:17 - You therefore, beloved, since you know this beforehand, beware lest you also fall from your own steadfastness, being led away with the error of the wicked.
2 John 1:8-9 - Look to yourselves, that we do not lose those things we worked for, but that we may receive a full reward. Whoever transgresses and does not abide in the doctrine of Christ does not have God. He who abides in the doctrine of Christ has both the Father and the Son.
Rev 2:4,5 - Nevertheless I have this against you, that you have left your first love. Remember therefore from where you have fallen; repent and do the first works, or else I will come to you quickly and remove your lampstand from its place—unless you repent.
Rev 3:5 - He who overcomes shall be clothed in white garments, and I will not blot out his name from the Book of Life; but I will confess his name before My Father and before His angels.
Rev 3:16-17 - So then, because you are lukewarm, and neither cold nor hot, I will vomit you out of My mouth. Because you say,‘I am rich, have become wealthy, and have need of nothing’—and do not know that you are wretched, miserable, poor, blind, and naked.
Taken from Wikipedia