If we are willing to honestly consider and follow the Truth of the word of God wherever it leads (which is not to the cult , then we should concede that God many times warns believers, as believers, against forfeiting what justifying obtained. Such as against developing an "evil heart of unbelief in departing from living God," from the faith they once held, falling from grace, making Christ of no effect, to no profit, drawing back to perdition," and yielding to pressure to deny the faith after conversion, so that Paul's labor would be in vain, (Gal. 5:1-5; Heb. 3:12-14; Heb. 10:25-31, Heb. 10: 38-39; 1 Thessalonians 3:5)
And because ye are sons [Paul's audience], God hath sent forth the Spirit of his Son into your hearts, crying, Abba, Father. (Galatians 4:6)
Stand fast therefore in the liberty wherewith Christ hath made us free, and be not entangled again [those who were set free] with the yoke of bondage [going back into what they were set free from]. Behold, I Paul say unto you, that if [submission to Judaizers these believers are being warned against] ye be circumcised [signifying justification obtained by keeping all the law], Christ shall profit you nothing. For I testify again to every man that is circumcised, that he is a debtor to do the whole law. Christ is become [an effectual change due to their choice] of no effect unto you, whosoever of you are justified by the law; ye are fallen from grace[their former state]. For we [those who continue to believe] through the Spirit wait for the hope of righteousness by faith. (Galatians 5:1-5)
Take heed, brethren, [contextually not a general sense, but as believers] lest there be in any of you an evil heart of unbelief, in departing from the living God [a departure from their former state s believers]. But exhort one another daily, while it is called To day; lest any of you be hardened through the deceitfulness of sin [a change of heart]. For we are made partakers of Christ, if we hold the beginning of our confidence stedfast unto the end [[perseverance of the saints]. (Hebrews 3:12-14)
Let us hold fast the profession of our faith without wavering [continued exhortation to persevere]; (for he is faithful that promised
And let us consider one another to provoke unto love and to good works: Not forsaking the assembling of ourselves together, [indicating departing from the faith, as follows] as the manner of some is; but exhorting one another: and so much the more, as ye see the day approaching. (Hebrews 10:23-25)
For if [a choice brethren are warned against] we [not just you] sin wilfully [not out of weakness, but with full consent, as a decision not to continue but to depart, signified by giving up being with the believers] after that we have received the knowledge of the truth [a term which refers to believing, as per 1Tim. 2:4; 2Tim. 3:7], there remaineth no more sacrifice for sins [cf. Hebrews 6:6-8; a terminal condition of judgment, with no provision for repentance and forgiveness, having forfeited what saving faith obtained], But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries. (Hebrews 10:26-27)
He that despised Moses' law died without mercy under two or three witnesses: Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified [a past condition, appropriated by faith, now forfeited by a definite denial of the same] , an unholy thing, and hath done despite unto the Spirit of grace? (Hebrews 10:28-29)
Cast not away therefore your confidence, [the issue being faith, out of which obedience flows] which hath great recompence of reward. For ye have need of patience, that, after ye have done the will of God, ye might receive the promise [not that doing earns the promise, but that saving faith is that which finally perseveres, which faith as manifested in works God - who gave faith and the ability and motivation to obey - rewards under grace] For yet a little while, and he that shall come will come, and will not tarry.
Now the just shall live by faith [the just live by faith, not merely profess it, with such faith being what appropriates justification]: but if any man draw back [a denial of justifying faith], my soul shall have no pleasure in him [as solemnly, fearfully described above]. But we [who do not draw back, but persevere] are not of them who draw back unto perdition [contextually a terminal condition of judgment, with no provision for repentance and forgiveness due to treating Christ with contempt] but of them that believe to the saving of the soul. (Hebrews 10:35-39)
But when we are judged, we are chastened of the Lord, that we should not be condemned with the world. (1 Corinthians 11:32)
For verily, when we were with you, we told you before that we should suffer tribulation; even as it came to pass, and ye know. For this cause, when I could no longer forbear, I sent to know your faith, lest by some means the tempter have tempted you, and our labour be in vain. (1 Thessalonians 3:4-5)
Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand; By which also ye are saved, if ye keep in memory [katechō: hold fast: cf. 1Ths. 5:21] what I preached unto you, unless ye have believed in vain. (1 Corinthians 15:1-2)
Such departing from the the living God, drawing backing into perdition, falling from grace, etc., is likely the the "great transgression," (Psalms 9:13) that of having "wickedly departed from my God,"(2 Samuel 22:22) which David stated he did not do, despite his sins, for unlike apostates he overall kept the ways of the Lord, and confessed in repentance when convicted of not doing so, (2 Samuel 12:7-13)
Note again that the above verses are clearly written to believers as believers, exhorting them to continue in the faith and warning against rejecting it, and thus these cannot be dismissed as never having been born again , although there are those who left fellowship since they were never in Christ. (1 John 2:19)