Sin is biblically defined as breaking/disobeying God's law.

With the #1 false gospel of today, people are taught that faith in Jesus alone will never save you at all whatsoever unless you "repent of your sins"

Some sects [cults] define repenting of your sins as never sinning again and will teach that you will KNOW you're finally saved once you realize you've now stopped sinning and no longer ever have even a bad thought and are therefore perfect and sinless like Jesus. These people are known as "sinless perfectionists".

Another way people will view it [i.e. as in, will see it/will make claims about it] is that faith in Jesus cannot and will not ever save you UNLESS you felt the proper, but undefined, amount of regret/remorse for every sin

So, for example, if you told a lie after believing in Jesus, but you forgot about it, then you died in a car crash you would go straight to hell because of that unrepentant sin. They'll say you COULD have been saved, but you didn't keep yourself saved because you forgot to feel remorseful for that sin making your faith in Christ through his death, burial, and ressurection, null and void. BUT of course, you'll never find these false gospels in actual Scripture. But if you're open to any and every new Bible version they come out with, you'll be met with countless contradictions and rewritten passages with entire passages missing, etc and you'll be susceptible to any lie.

The Bible makes it crystal clear that eternal life is eternal and of all that Jesus receives he will lose none and he will never leave us nor forsake us

When people teach against this fact they use passages that aren't about eternal life/salvation but are rather about the consequences we receive in the flesh.

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📖 1 John 3:4 [New Testament] ¹⁶¹¹ᐟᴷᴶⱽ 📖
⁴ Whosoeuer committeth sinne, transgresseth also the lawe: FOR SINNE IS THE TRANSGRESSION OF THE LAW.

📖 Romans 3:19-23 KJB 📖
Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God.
Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin.
But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets;
Even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe: for there is no difference:
For all have sinned, and come short of the glory of God;

📖 James 2:10 KJB 📖
For whosoever shall keep the whole law, and yet offend in one point, he is guilty of all.

ℝ𝕖𝕡𝕖𝕟𝕥𝕒𝕟𝕔𝕖 𝔼𝕩𝕒𝕞𝕚𝕟𝕖𝕕