Meaning that it's possible, after conversion, never to sin again (and thus earn salvation)??
Not all sin is the same. There are grievous sins that lead unto spiritual death, and there are minor infractions or hidden faults that do not lead to spiritual death.
Grievous sin is another name for a "
sin unto death"
(Note: To check out the reference to the "sin unto death," see: 1 John 5:16).
(i.e. death = spiritual death or the second death) (Note: The second death is destruction in the Lake of Fire - Revelation 21:8).
"And the LORD said, Because the cry of Sodom and Gomorrah is great, and because their sin is very grievous;" (Genesis 18:20).
Examples of Grievous Sin:
#1. Not loving God, and not loving your neighbor (For loving God and loving your neighbor is a part of eternal life; See: Luke 10:25-28 cf. Matthew 19:17-19; Not loving Jesus (God) means one is accursed, see: 1 Corinthians 16:22; As for not loving your neighbor, see the Parable of the Good Samaritan (Luke 10:29-37), and then see number #5 below).
#2. Looking at a woman in lust = danger of being cast bodily into hell fire (Matthew 5:28-30).
#3. Not forgiving = not being forgiven by the Father (Matthew 6:15).
#4. One can be condemned by their words (Matthew 12:37).
#5. Not helping the poor or the unfortunate = Going away into everlasting punishment (or everlasting fire) (Matthew 25:31-46).
#6. No man who puts his hand to the plow (i.e. one who spreads the gospel and teachings to lead men of God into holiness by His Word) and looks back (turns away from doing so) is fit for the Kingdom of God (Luke 9:62) (Note: See the KJV rendering on this verse).
#7. 1 John 3:15 says, "Whoever hates his brother is a murderer: and you know that no murderer has eternal life abiding in him."
#8. Galatians 5:19-21 says, "Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness, Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies, Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God." Meaning, those who do these kinds of sins will not inherit (enter) God's kingdom (i.e. they will not be saved). For entering God's kingdom is associated with salvation in Matthew 25:34 (Note: Paul is mentioning the violation of the Moral Law. The Moral Law is the same equivalent as loving your neighbor; See Romans 13:8-10).
#9. But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death. (Revelation 21:8).
Minor infractions or
faults of character is another name for a "
sin not unto death" (i.e. not unto death = not unto spiritual death or the second death) (Note: While the "sin not unto death" mentioned in 1 John 5:17 is in context to confessed sin in John's epistle (See: 1 John 1:9), it can be extended loosely to refer to the kind of sins that do not lead to spiritual death by it's very name).
"Who can understand his errors? cleanse thou me from secret faults."
(Psalms 19:12).
Examples of Sins That Do Not Lead Unto Spiritual Death:
#1. 1 John 5:17 mentions the "sin not unto death."
In context to
1 John 5: This would be talking about confessed grievous sin that one is striving to overcome with the Lord's help (1 John 2:1) (1 John 1:9) (Romans 13:14). In
1 John 5, the brethren are praying for this believer to have victory (life) over their sin as this believer confesses their sin (Note: Grievous sin are sins the Bible warns with punishment by hellfire, or spiritual death, etc.; These would be sins like murder, hate, adultery, theft, idolatry, etc.). If these sins are confessed with the intention of forsaking them, the individual is not abiding in spiritual death.
#2. Psalms 19:12 says, "Who can understand his errors? cleanse thou me from secret faults." I believe these would be faults of character or minor errors that a person might make with people. Example: A person may not be a great listener, and they do not allow others to speak like they should. By not listening to others may come off a little like they do not care (even though they care in their own way or a different way). Paul wanted to go to Jerusalem. The Spirit warned Paul not to go. He was still determined to go because he loved His fellow Jews and wanted them to know the love of Jesus. The Spirit told the brethren that Paul will be imprisoned by his going to Jerusalem. The brethren warned Paul not to go. They were in tears and loved him and begged him not to go. But Paul did not listen. He would not hear them. He did not want to hear it. Fault of character. Hidden fault. Minor error of his character. It is not something that condemned him (See
Acts of the Apostles 21, and read this article
here by Ray Stedman; Note: There is even a better write up than this one by Bible commentator James Boice
here; Please keep in mind I do not share their views on Soteriology, though; I merely agree with their view on what happened with Paul in
Acts of the Apostles 21).
#3. The Command to Be Baptized.
Paul says Christ sent him not to baptize but to preach the gospel (
1 Corinthians 1:17). If it was essential to salvation, then why would Paul say something like this? In
1 Peter 3:21: Peter says baptism is not for the putting away of the filth of the flesh. If you were to turn to
2 Corinthians 7:1, you would see that it uses similar wording ("filthiness of the flesh") that is clearly in reference to sin. So Peter is saying that baptism is not for the putting away of "sin" [i.e. filth of the flesh]. In other words, baptism is not a command that if disobeyed, leads to spiritual death.
#4. Other Commands in the New Testament that do not seem like a major violation of loving God and loving your neighbor that have no death penalties attached to them. One example would be the command to Rejoice when men persecute you or falsely accuse you of evil in
Matthew 5:11-12.
Real world examples: Going 5 miles per hour over the speed limit in area that is not life threatening to others. Not taking out the trash yesterday when it was a little stinky. These minor transgressions would obviously not send a Christian to hell.
But we as Christians strive to obey and do good in all things in the Lord. We strive to keep His commandments. For it is written,
"For this is the love of God, that we keep his commandments: and his commandments are not grievous.' (1 John 5:3).
Side Note:
Please understand that it is not possible for a person to obey God's commands without them first being saved by Jesus Christ and His grace (i.e. by seeking forgiveness of their sin with Him, and believing in His death, and resurrection on their behalf). For Christians are initially and ultimately saved by Jesus Christ.