Since Christ did not intend to make a list of laws to follow, how do we know what's sinful? Clearly Christ in scripture did not teach that we could live sinful lives and be in Him, but He did teach an end of the Laws salvation authority. But clearly by scripture, the Law and sin are not a one to one correlation. Paul plainly taught that the uncircumcised weren't committing sin at all (he didn't suggest they go get circumcised now). So, if not plainly stated as the law was, how do we know what's sinful since it was not Christ's intent to make a list to follow?
Galatians 1:1 - 24
ESV - 1 Paul, an apostle - not from men nor through man, but through Jesus Christ and God the Father, who raised him from the dead - 2 And all the brothers who are with me, To the churches of Galatia:
Community answers are sorted based on votes. The higher the vote, the further up an answer is.
In my opinion, for Christians (as you say), the Law no longer has salvation authority, since Christ fulfilled the entire Law on their behalf. Christians are thus not granted salvation on the basis of obedience to the Law, but through faith in Jesus' atoning death and resurrection. Also, certain requirements of the Law (such as its sacrificial, ceremonial, and civil aspects, as well as circumcision) were meant to apply only to Israel, or to point forward to Jesus' ultimate sacrifice, and have become obsolete for Christians. However, in my opinion, the moral portion of the Law (as given in the Ten Commandments (Exodus 20); as amplified by Jesus in the Sermon on the Mount (Matthew 5) and summarized by Him in Matthew 22:37-38; and as mentioned by Paul in Romans 13:8-10) still constitutes a valid indication for Christians as to how God wants them to use their new freedom to express their gratitude to God for their salvation, and to glorify Him. Christians will not lose their salvation by violations of the moral law, but they should still confess those violations to God and receive His forgiveness for Jesus' sake, in order that their fellowship with God may not be adversely affected. In my opinion, God will also use Christians' degree of obedience to the moral law as a basis for the granting of eternal rewards to them. (Paul referred to this in 1 Corinthians 3:11-15.)
All know good and evil thanks to Adam & Eve (Gen 3:5) unless you have seared your conscience (1 Tim 4:2). Some of the Gentiles, not having the law, kept the law not knowing it, give testimony that they understood wright from wrong. Rom. 2:12-15 For as many as have sinned without law will also perish without law, and as many as have sinned in the law will be judged by the law (for not the hearers of the law are just in the sight of God, but the doers of the law will be justified; for when Gentiles, who do not have the law, by nature do the things in the law, these, although not having the law, are a law to themselves, who show the work of the law written in their hearts, their conscience also bearing witness, and between themselves their thoughts accusing or else excusing them) What the law did was to impart knowledge of sin to the nation of Israel. However keeping the law did no justify anyone in God's sight. The law was given to stop every mouth and find the world guilty, demonstrating that all needed a Savior. (Rom 3:19-20) All Christians have the Holy Spirit within that will guide them in all truth (John 16:13) and God's Word the ultimate resource of truth to guide and sanctify them. John 17:17 Sanctify them by Your truth. Your word is truth. 2Tim. 2:15 Be diligent to present yourself approved to God, a worker who does not need to be ashamed, rightly dividing the word of truth. Eph. 1:13 In Him you also trusted, after you heard the word of truth, the gospel of your salvation; in whom also, having believed, you were sealed with the Holy Spirit of promise, 1 Th. 2:13 For this reason we also thank God without ceasing, because when you received the word of God which you heard from us, you welcomed it not as the word of men, but as it is in truth, the word of God, which also effectively works in you who believe.
There is much confusion in the Christian world regarding The Law and Grace through our Lord Jesus Christ. Jesus did not come to destroy The Law. He said in Matt. 5:17, that He had not come to destroy the Law or the Prophets, but to fulfill it, and that not one tiny bit of the Law would pass away, even until heaven and earth passed away. Paul explains in Romans 7 and in Galatians 3 that The Law was like a school master, showing us what sin looks like. The Law is holy, just and good, but shows us what indwelling sin is. The Law in itself does not have the power to free us from sin, only the blood of Christ can do that, which removes the curse of the Law. So Jesus came to destroy The Curse of the Law, (Deut 11:26-28, Gal 3) and The Works of the Law. (Eph 2:8-10) Gal 3:31 says that we do not destroy the Law through faith, but establish the Law through faith in Christ. And now that the Spirit of Christ has come, as we keep our spirit in tune with Christ we are compelled in our Spirit to stay in step with God's Law. We can still look at the list of commandments and know that these are sins, but the indwelling Spirit of Christ will guide us into the truth of how to keep ourselves pure from these sins. Paul did not teach that the uncircumcised (Gentiles) were not sinning, (Romans 2) but that if they have enough conscience to obey the Law, even without knowing the Law, then how can the circumcision (the Jew) who God had entrusted with the Law, have any excuses at all? But through Christ, God has joined both Jews and Gentiles to live, not by the Works of the Law, but by the Spirit of Grace.
This question is asked about "christians" but I don't think christians have any special powers to detect sin that muslims, hindus, buddhists, atheists or anybody else doesn't have. Sin is described in scripture as being unmistakable. Adam and Eve knew immediately after their faux pas that they'd messed up (Genesis 3:7) How do you know if something is hot? You don't have to touch it, getting too close can do the trick. You go by how it feels. That doesn't work for sin. It can feel right and still be sinful. I've seen a question on this site where a person asked 'how could it be wrong for the way they feel about loving someone if they've felt that way all of their lives.' I'm not trying to answer that here. The law can't be your guide either. Laws are different in different places. Wrong is wrong worldwide. The law said that if a man died without his wife bearing children one of his brothers was to marry his wife and raise up children in his stead for him. It was considered the right thing to do (Deut 25:5, Mark 12:19). This wouldn't have felt right for me. I could have never slept with either of my two brother's wife whether they'd passed on or not. It might not have been sin per se but that wouldn't have changed the way I felt about it. I and my two brothers are too close for such as that to happen. There's the Law, sin, and then there's what we know to be wrong. I don't think wrong escapes us. Paul said 'All things are lawful for me, but all things are not helpful'(1Cor 6:12). I think he means that just because he is not under a law doesn't mean he's going to just "let it all hang down," the way Eric Clapton said he does after midnight. Sin never disguised itself good enough for me to not recognize it when I looked forward to "after midnight." Maybe it does for others, but not me. What I discovered was something much more important than whether or not something was considered sinful or not, but what the things that are sinful are really like. The serious nature of sin is what the Lord opened my eyes to. The way the prophet Amos said it is what is usually true for the list of people who I gave labels to in the beginning of my answer here. It was true for me until the Lord saved me. "I sent among you a plague after the manner of Egypt; Your young men I killed with a sword, I also captured all your horses; I made the stench of your camps come up into your nostrils; yet you have not returned to me (Amos 4:10). The stench of sin is unmistakable. If you're confused about such things as whether or not cutting your grass on a certain day of the week is wrong or not, that's one thing. You'll have to wrestle with God about that on your own, I don't get involved with such matters. But if you want to know if you should lie on your application to get a loan or a job your conscience will help. Someone mentioned a seared conscience in their answer. A seared conscience is like a cell phone with the alert volume turned off. It still vibrates, however. And all you need to do to start back getting alerts is press the up volume button on the side of the phone. The conscience can't be removed, but if ignored long enough, it'll stop getting your attention. I've heard people say 'listen to your heart.' That, for sure, ain't in the bible. "The heart is deceitful above all things, and desperately wicked; who can understand it"? (Jeremiah 17:9). You can't trust your feelings, your heart will deceive you, and the law is obsolete for a believer. What's a believer to do? For in it (the gospel) the righteousness of God is revealed from faith to faith; as it is written, "BUT THE RIGHTEOUS man SHALL LIVE BY FAITH." (Romans 1:17)
All answers are REVIEWED and MODERATED.
Please ensure your answer MEETS all our guidelines.
A good answer provides new insight and perspective. Here are guidelines to help facilitate a meaningful learning experience for everyone.