I have one question for you. Do you believe in sin, . . .
Since I regularly confess my sins, I guess I must.
and if so, what is “sin”?
Well, you seem to have missed my distinction, amun. You obviously equate sinning to breaking a commandment (legalism) as opposed to rupturing one’s relationship (covenantal love) in righteousness (what is BEHIND the commandment) with the Righteous One; this rupturing is sin because it breaks our bond of love with God to lesser or greater extents.
I do not say that Christians are allowed to steal, commit adultery, etc, e.g., God forbid! Those things are terrible sins; but, there is a difference between being bound to do something (or not to do something) as a matter of law, versus being bound to do something (or not to do something) as a matter of a Covenant of Love. For example: It is wrong for a man to cheat on his wife. Now, until very recently, in many American states, it was actually a criminal offense to commit adultery - a violation of the law. And, still today, if a woman divorces her husband for adultery, the law will award her for damages, etc. But, should a man avoid cheating on his wife just because of these laws??? Of course not. A man should not cheat on his wife because he loves her and has a covenant of love with her. See the distinction?
It is one thing to be in a Covenant based on Law (the Old Covenant) but quite another thing to be in a Covenant based on Love (the New Covenant). In both Covenants, something like adultery is forbidden. But, in the Old Covenant, one avoided committing adultery because it was a violation of the Law that subjected you to punishments. In the New Covenant, one avoids adultery because it violates the Covenant of Love between you and Jesus Christ, and outside of that Covenant of Love there is no salvation for you, or anyone. This is an important distinction, because it personalizes our Covenant with God. We do not do righteous things merely because we’re scared of the Law and its punishments, and so do what the Law demands. Rather, we do righteous things because we are in a Covenant of Love with Jesus Christ (He Who enables us to live righteously in the first place by His grace!), and we do not want to ruin this Covenant (this “friendship” or love relationship) with Him. This is why St. Paul, in Romans 3:28, says that Christians are saved “by faith and not by the works of the Law.”
Now, as for the Ten Commandments themselves: As I said, we are not bound by them as a matter of LAW. Rather, we are bound by the righteousness behind these Commandments, which is the Righteousness of the Person of Jesus Christ, Who we are called to be like in all things. What this means is that we need to go beyond the mere letter of the Ten Commandments so as to keep the righteousness behind these (legal) Commandments perfectly. Jesus Himself tells us this in Matthew 5, where He says, in regard to adultery, for example (Matt 5:27-28):
“You have heard that it was said, ‘You shall not commit adultery.’ But I say to you, everyone who looks at a woman with lust has already committed adultery with her in his heart.”
Likewise, in regard to the Commandment against murder (Matthew 5:21-23), Jesus says:
"You have heard that it was said to your ancestors, ‘You shall not kill; and whoever kills will be liable to judgment.’ But, I say to you, whoever is angry with his brother will be liable to judgment, and whoever says to his brother ‘Raqa’ (i.e., “Fool!’ - a specific curse in Aramaic) will be answerable to the Sanhedrin, and whoever says, ‘You fool,’ will be liable to fiery Gehenna.”
Jesus says other, similar things in this same passage, but, the teaching is clear: Under the Mosaic Law, people were forbidden to commit adultery and murder; however, Jesus (in the New Covenant) requires us to go further than that. For, under the Old Covenant, people would only keep the letter of these Laws and not go any deeper than that …because nothing required that they do so. For example, the Commandment “Thou shall not kill” was limited to the legal wording of the Commandment. According to the Pharisees, as long as one kept the specific legal conditions of the Commandment, one was “righteous before God.” Jesus denies this; for the Lord Jesus, the mere letter of the Law is not enough, for, while the Commandment says, “Thou shall not kill,” it does not mean that you are righteousness if you just beat a man within an inch of his life, just as long as you do not actually kill him.

That was never God’s intention at all; rather, the Commandment goes much deeper than that, and Christians are obligated (by their Covenant of Love with Jesus Christ) to keep the Commandment much deeper than that. However, non-Christian Jews are not. They are only bound by the specific wording of the Commandment - that is, they are bound by the letter of the law, and on a mere basis of law. Christians are bound by the righteousness of Christ Himself (to Whom the Law points) because of their Covenant of Love with Jesus Christ. See the distinction?
continued. . .