Heck, if someone wants to keep the kosher laws, you're probably not going to be able to dissuade them. More power to 'em. Keeping kosher is actually a pretty healthy way to eat and to live, but for your own edification, and because you asked politely, here are a few verses that satisfy me on my freedom from the dietary laws -- actually on pretty much the whole shebang:
Peter went up on the roof to pray. He became hungry and wanted something to eat, and while the meal was being prepared, he fell into a trance. He saw heaven opened, and something like a large sheet being let down to earth by its four corners. It contained all kinds of four-footed animals, as well as reptiles of the earth and birds of the air. Then a voice told him, "Get up, Peter. Kill and eat."While this is part of the passage dealing with God calling on Peter to take the gospel to the Gentiles, note that the vision specifically deals with food. In fact, it's only after Peter accepts that the dietary restrictions have been superceded that he's willing to visit the house of Cornelius.
Surely not, Lord!" Peter replied. "I have never eaten anything impure or unclean."
The voice spoke to him a second time, "Do not call anything impure that God has made clean."— Acts 10:9-15
The church council in Jerusalem also settled the issue of Gentiles following the Torah in its letter to the Gentile churches:
We have heard that some went out from us withotu our authorization and disturbed you, troubling your minds by what they said. So we all agreed to choose some men and send them to you with our dear brothers Barnabas and Paul ... It seemed good to the Holy Spirit and to us not to burden you with anything beyond the following requirements: You are to abstain from food sacrificed to idols, from blood, from the meat of strangled animals and from sexual immorality.Of course, that didn't satisfy the group Paul called the Judaizers, and in several epistles he was forced to address the issue himself. One of his more strident passages says:— Acts 15:23-20
You foolish Galatians! Who has bewitched you? Before your very eyes Christ was clearly portrayed as crucified. I would like to learn just one thing from you: Did you receive the Spirit by observing the law, or by believing what you heard? Are you so foolish? After beginning with the Spirit, are you now trying to attain your goal by human effort? Have you suffered so much for nothing -- if it really was for nothing? Does God give you his Spirit and work miracles among you because you observe the law or because you believe what you heard?In other words, observance of the Torah — including dietary law — is not required of a believer; we are expected to live by faith and the Spirit, which frees us from being enslaved to doing "the right thing." Put another way: I push all the little old ladies in front of cars that I want, rob all the banks I want, and have all the adultery I want. Of course, when you are living by faith and the Spirit, none of those things should appeal to you very much.
Consider Abraham: "He believed God, and it was credited to him as righteousness. Understand, then, that those who believe are children of Abraham. The Scripture foresaw that God would justify the Gentiles by faith, and announced the gospel in advance to Abraham: "All nations will be blessed through you." So those who have faith are blessed along with Abraham, the man of faith.
All who rely on observing the law are under a curse, for it is written: "Cursed is everyone who does not continue to do everything written in the book of the Law." Clearly no one is justified before God by the law, because "The righteous will live by faith." The law is not based on faith; on the contrary, "The man who does these things will live by them." Christ redeemed us from the curse of the law by becoming a curse for us, for it is written: "Cursed is everyone who is hung on a tree." He redeemed us in order that the blessing given to Abraham might come to the Gentiles through Christ Jesus, so that by faith we might receive the promise of the Spirit.— Galatians 3:1-12
Remember that the Torah and all its dietary restrictions came to the Jewish people at the time of Moses. There is no reason to believe that Abraham observed the kosher laws, although it is possible that some of those laws developed during the period of Israel’s enslavement to Egypt and later received divine sanction after the exodus. In any event, the Scriptures are quite clear that we can eat pork and shellfish — that we can even eat pork roll and cheese on a bagel — and have a solid relationship with God.
In another of his letters, Paul has the following to say specifically about food:
Therefore, do not let anyone judge you by what you eat or drink, or with regard to a religious fetival, a New Moon celebration or a Sabbath day. These are a shadow of the things that were to come; the reality, however, is found in Christ.As I said earlier, I doubt any of this will change your correspondents’ minds. Generally, when people have made their minds up that strongly, they don’t want to acknowledge the validity of other interpretations and will just get more recalcitrant if you push the issue. My advice is to let them think what they want, and if you’re concerned that they’re in danger of shipwrecking their faith or that of others, that you pray for them. In a truly extreme case, you might want to consider blocking them from the forum, though it doesn’t sound like it’s that bad at this point.— Colossians 2:16-17