Common misunderstanding here.
It is increasingly common on this sub for people to get hung-up on Old Testament laws as if they are still applicable today. They are not. They are a guide for us to understand God, but they are not to be applied in any strict manner - especially with a pick-and-choose mentality. Here's why.
FIRST
The Old Testament laws were written for the Israelites living in Israel in a thousands-year-old culture. If you are Jewish and actually live in Israel today, then by all means, follow your conviction. But even then I think modern Israel doesn't even mandate adherence to biblical laws, as they have their own independent justice system. Regardless, for everyone else, trying to apply ancient Israeli law today is like telling a guy in New York that he should go to jail because he broke Japanese law. It just makes no sense and it's the wrong legal standard.
SECOND
Even if you are living in Israel, if you're a Christian you're set free from the law. This is why Paul can explain in Philippians 2 how before Christ he was the best Jew of all the Jews, and yet in 1 Cor. 9:20 say, "To the Jews I became like a Jew, to win the Jews. To those under the law I became like one under the law (though I myself am not under the law), so as to win those under the law."
THIRD
Some people like to distinguish between "moral, civil, and ceremonial laws." The Bible itself does not make this distinction. This is a human philosophy created by people who wanted to rationalize keeping some laws while ignoring others. Leviticus 19 is a perfect example of this. It hops all over the place from moral to civil to moral to ceremonial to civil to whatever without any linguistic or other distinguishing factor separating the laws.
Consider verse 18: "love your neighbor as yourself." The very next verse talking about breeding cattle and not wearing cloth with two kinds of material. Are we saying that verse 18 is kept but 19 is cut? On what basis? Even if the moral, civil, ceremonial distinction is legitimate - where is the standard God gave for letting us know which is which? We can't just look to the 10 commandments because the second greatest command, which Jesus endorsed, isn't even in there. So how else do we know to create a distinction? There is no standard and any attempt to create one is based on human philosophy and rationalization, not Scripture. Don't fall into that trap.
FOURTH
Some people like to point to Jesus saying, "Until heaven and earth pass away, not an iota, not a dot, will pass from the law until all is accomplished" (Matthew 5). That doesn't mean the law will continue to apply until heaven and earth pass away - it means that the law will exist indefinitely until all is accomplished. When is that? He said it in the previous verse: when he would fulfill the law. It reads like this: "I'm here to fulfill the law. The law won't go away until I accomplish that fulfillment."
It's like if I executed a contract that said, "This promissory note shall have no expiration date. Bob shall continue paying on his debt until it is paid in full." Does that mean that after Bob has paid his debt in full he has to keep paying it just because there's no expiration date? Obviously not. The contract didn't expire, but it has been fulfilled. When the "until" condition is accomplished, the expiration date is rendered moot. Sure, it's still a valid agreement, but because the condition is satisfied there is never a situation where anyone can be sued on the agreement anymore. So, it's not a void agreement - it's merely a moot one that can never be brought up in court again.
In the same way, when Jesus was on the cross and said, "It is finished," that's when "all is accomplished." The condition was fulfilled and the law thereby rendered moot. Hebrews 8 and 9 specifically reference this as the time when the old covenant was made obsolete. 8:13 says, "By calling this covenant 'new,' he has made the first one obsolete." The old covenant was of the law and obedience. The new covenant is of grace through faith.
FIFTH
I'd have a hard time trying to count the number of times in the NT Paul tells people they're not under the law and that they should not obligate anyone else - especially Gentiles - to follow the Old Testament law. The only instance where we see Old Testament law being imposed on Gentiles is from Acts 15, and this was made as a concession to maintain the peace, not as a theological mandate. Even at that, in passages like Romans 14 and 1 Cor. 8 we see that Paul eventually abandoned this concession and preached that some of the things that council forbade really weren't theologically wrong, thereby proving it was only a concession and not a theological conclusion. But even for those who do want to treat this as a theological conclusion, many of the Old Testament commands the church often holds over people's heads today were not among the 4 things listed.
SOLUTION
So what are we to do with all of this? What's the point in the Old Testament, then?
As I noted above, it's like someone telling a New Yorker that he should be convicted for breaking Japanese law. Obviously that conviction will never stand if his crime wasn't committed in Japanese jurisdiction. Even worse - if it's ancient Japanese law that even the Japanese don't utilize anymore. But what's important to recognize here is that the guy who wrote all of the laws applicable to a New York citizen is the exact same guy who wrote those ancient Japanese laws.
Why is that relevant? It doesn't mean he'll judge by his old laws. But it does give us significant insight into the nature of the guy who created the laws and the probable intent he had behind establishing the system he created in New York. Make sense? So, if there's a dispute as to what the New York law-maker meant when he set up the New York system, we can reference how he used to do things in Japan to gain insights as to the proper interpretation of our present situation.
EXAMPLE
Lots of people want to point to Leviticus 19 and say, "There's definitive proof that homosexuality is sin!" Other people will point to NT passages, like Romans 1, and show how it references homosexuality as sinful. These are horrible explanations. All it does is attempt to revive the old covenant - telling people to live by a legal code rather than explaining how application of this view fits within the covenant of grace through faith. Let me be clear about this: even if you can convince a homosexual person to stop committing homosexual acts, this will not save them. So, what's the point of trying to decrease the sin of a non-believer who can do nothing but sin anyway?
For those who are saved, our obligation is not to a written code. If we are a new creation - a creation fashioned in the image of Christ, which is why we are called Christ-ians - then our only obligation is to live in light of the creation we were made to be. In Genesis we know that we were originally designed to reflect God's image. That image was broken. Because of Christ, it is restored. Our obligation to God is not to the law itself; rather, it is to uphold that restored image that he gave us. The law was only given after the image was broken, which is why it is irrelevant to someone who has been restored in their capacity to uphold that image. As noted above, the law can be a guide to help us figure out what that image looks like, but the image of God is the point, not the law for its own sake.
By looking at life as a reflection of God's image, we can actually achieve an independent conclusion as to the sinfulness of something without needing to reference it as a legal imperative. The law is no longer our master, thus we should not rely on it to justify anyone, as if telling a homosexual to stop having homosexual sex will somehow save them. Only Jesus saves. Here's how this can work in a series of examples.
Homosexuality
Physical marriage is meant to reflect the spiritual marriage God has with his people. God designed in creation specific roles to be followed by the husband and wife in the context of physical marriage, which reflect the roles that God wants lived out in the context of his relationship with his people. When physical marriage is between two grooms or two brides, we are no longer reflecting to the world the type of relationship that God wants with his people. It reflects a false image. As homosexuality increases, the parallel God is trying to establish inherently decreases.
Taking it a step further, it also means that those within a homosexual relationship have no personal frame of reference for experiencing the type of relationship that God wants with them. They also lose their ability to teach the proper type of relationship to others - because the parallel is broken. Two homosexual men will have a hard time explaining what it looks like to be the bride of Christ. Two homosexual women will have a hard time understanding what it is like to be a follower to our bridegroom, who is Christ.
To go a bit deeper Malachi 2:15 also says that the purpose of God making two people one flesh is to produce godly offspring. Because homosexuals cannot biologically reproduce, if we embrace homosexual marriage we are communicating to the world that spiritual reproduction with our spiritual spouse is not important either - because our physical behaviors reflect on the spiritual character and intentions of God. Accordingly, homosexual marriage undermines the importance of our mission to make disciples and would lead to the conclusion that God is also okay with having an unfruitful relationship with his people.
Lying
Let's take another easy example. If we are to bear God's image to the world, what would it say of God if we, his image-bearers, were liars? It would communicate to the world that God is also a liar. If God is a liar, he cannot be trusted and his professions of salvation to all who believe lose their potency. The Gospel is undermined and even the genuine believers have no good faith basis for putting their trust in a lying God.
Premarital Sex
Here's another biggie. Throughout most of history, sex was about reproduction. Effective contraception is a relatively new phenomenon. If we bear God's image, then engage in premarital sex, we are reflecting to the world that God is okay with reproduction outside of marriage. To follow the parallel of God's interaction with his people, it's as if we are telling the world that you don't need to have a committed relationship with Jesus - you can get all the same benefits of marriage to Christ without needing genuine faith, and that God will even use you to produce spiritual children to raise and entrust them to your care, even if you're not part of his bride, the Church. But we know from Scripture (Matthew 7 most notably) that this is wrong and God does not function this way. So, engaging in premarital sex as a person who professes to bear God's image is reflecting the wrong image of God to the world.
Stealing
If we bear God's image and we steal, then we're communicating to the world that God is also a thief. He might take from others what does not belong to him. Now this is a pretty idiotic idea because everything belongs to God, so God can't steal in the first place; he can only recover. But even with that thought aside, God has intentionally given people a certain modicum of security in ownership and autonomy. The entire basis of our perception of salvation is founded on this concept. If God were a thief who showed no concern for our autonomy, then how could we rely on the good things he claims to give us? He might give us salvation and heaven, but he might take it away too. That's not a helpful image of Christ to reflect to the world.
CONCLUSION
Hopefully with the examples you can better see that the things we call "sin" are not wrong because the law says so. They are wrong because we were created by God to reflect his image and these behaviors fail to do that. They reflect a false image.
This is why Jesus says to check the plank in your own eye before looking at the speck in someone else's. Why? Because it's not about the sin itself. It's about God's image being shown to the world through us. This is how we bear fruit for his kingdom. It is how we reconcile all things in the world to him. It is how we share our faith - by our testimony of how we have been transformed into God's image and are being refined in that image day by day.
This is why Paul says in Romans 14:23 that everything that does not come from faith is sin. It's not because the label "sin" matters; rather, he's demonstrating that our lifestyle is what matters - that our lifestyle is born from faith to reflect God's image to the world. The technicality of one action or another means nothing. The reason for which we live and the way we reflect that reason to the world - that is what matters and that is what defines sin. It is also why Paul said a few verses earlier that nothing is inherently unclean - rather it is only unclean if we regard it as such. Because the specifics of one sin or another aren't the point. What our lifestyle reflects to the world about God is the point. That's what matters.
Posted May 23, 2018, 5:05 PM UTC