How?
If they weren't believers in the first place, they were never sealed with the Holy Spirit?
Just because some people go through the motions, doesn't mean they were saved. Even the demons believe and tremble. They certainly aren't saved.
Simply believing that God exists and wanting to go to heaven, and even working to go to heaven, saying all the right words, going to church, giving, doing, doing, doing, isn't going to get anyone anywhere.
It needs a born from above, born again, change of heart and life.
And when it happens, you know it. EVERYTHING about you changes. Anyone who hasn't had a point where they can look and see a point where they have had a God encounter that resulted in an inward change in thought, attitude, desire, etc, needs to consider whether they are really saved.
You cannot have the indwelling presence of the Holy Spirit in your life and not know it.
He does not seal us against our will. When we repent and turn to Him and trust in Him, He does seal us as we will. HE is faithful even if we are faithless.
If it were up to us to keep our salvation, I doubt many would make it. And He knows that. That's why I'm grateful that HE seals us and protects that which I have entrusted to Him.
Therefore leaving the principles of the doctrine of Christ, let us go on unto perfection; not laying again the foundation of repentance from dead works, and of faith toward God, Of the doctrine of baptisms, and of laying on of hands, and of resurrection of the dead, and of eternal judgment. And this will we do, if God permit. For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, And have tasted the good word of God, and the powers of the world to come, If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame. For the earth which drinketh in the rain that cometh oft upon it, and bringeth forth herbs meet for them by whom it is dressed, receiveth blessing from God: But that which beareth thorns and briers is rejected, and is nigh unto cursing; whose end is to be burned. But, beloved, we are persuaded better things of you, and things that accompany salvation, though we thus speak. For God is not unrighteous to forget your work and labour of love, which ye have shewed toward his name, in that ye have ministered to the saints, and do minister. And we desire that every one of you do shew the same diligence to the full assurance of hope unto the end: That ye be not slothful, but followers of them who through faith and patience inherit the promises.
This charge I commit unto thee, son Timothy, according to the prophecies which went before on thee, that thou by them mightest war a good warfare; Holding faith, and a good conscience; which some having put away concerning faith have made shipwreck: Of whom is Hymenaeus and Alexander; whom I have delivered unto Satan, that they may learn not to blaspheme.
Of these things put them in remembrance, charging them before the Lord that they strive not about words to no profit, but to the subverting of the hearers. Study to shew thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth. But shun profane and vain babblings: for they will increase unto more ungodliness. And their word will eat as doth a canker: of whom is Hymenaeus and Philetus; Who concerning the truth have erred, saying that the resurrection is past already; and overthrow the faith of some. Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his. And, Let every one that nameth the name of Christ depart from iniquity. But in a great house there are not only vessels of gold and of silver, but also of wood and of earth; and some to honour, and some to dishonour. If a man therefore purge himself from these, he shall be a vessel unto honour, sanctified, and meet for the master's use, and prepared unto every good work. Flee also youthful lusts: but follow righteousness, faith, charity, peace, with them that call on the Lord out of a pure heart. But foolish and unlearned questions avoid, knowing that they do gender strifes. And the servant of the Lord must not strive; but be gentle unto all men, apt to teach, patient, In meekness instructing those that oppose themselves; if God peradventure will give them repentance to the acknowledging of the truth; And that they may recover themselves out of the snare of the devil, who are taken captive by him at his will.
How would you know ? Can you read the seal ? Can you prevent God from breaking the seal to cut off the disobedient who turn from the faith ? Whosoever believeth that Jesus is the Christ is born of God:
It’s not even our faith that we rely on, it’s Christ’s faith within us.
Look at the text below. Notice that it’s not “our” faith but Christ’s faith in us that we live.
Paul says, “I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith OF the Son of God, who loved me, and gave himself for me.” (Galatians 2:20 AV)
It is Jesus’ faith working in us who believe. So, we see that our righteousness is not IN Christ, but OF Him. And if so, we become part with Him, and He IN us.
But of him are ye in Christ Jesus, who of God is made unto us wisdom, and righteousness, and sanctification, and redemption: That, according as it is written, He that glorieth, let him glory in the Lord. (1 Corinthians 1:30-31 AV)
“Being filled with the fruits of righteousness, which are by Jesus Christ, unto the glory and praise of God.” (Philippians 1:11 AV)
And be found in him, not having mine own righteousness, which is of the law, but that which is through the faith of Christ, the righteousness which is of God by faith: (Philippians 3:9 AV)