If any couple were justified in living together, it certainly would have been Adam and Eve. After all, there were no other options. Also, they didn’t know about adultery or fornication because those sins didn’t exist yet. Thirdly, they were in the truest sense ‘made for each other’. How interesting, though, that God didn’t see it like that. Instead, He uses their relationship as a perpetual pattern of His design for the human race. Jesus confirmed this because when He was confronted about the divorce issue, He went right back to God’s original plan in Genesis.
Throughout the centuries mankind has tried to alter God’s design with customs endorsing such things as polygamy. Modern liberals reject the sanctity of marriage and reduce this holy union to a piece of paper. Our immorally-based society embraces people living together; however, God doesn’t. Social or cultural acceptance of unholy alliances do not make them correct. Sadly, many Christians are following the world’s way rather than the way of the Lord. Plainly stated, for a Christian to be living with a member of the opposite sex, whether or not that other person is saved, is unscriptural, unholy, and ungodly. There is simply no justification for it. It makes a poor witness for Jesus Christ, and certainly gives an appearance of evil.
In contrast, marriage is a type of Jesus’ relationship with His bride, the Church. Being a Christian is not a ‘piece of paper’ relationship with our Lord, but an intimate, heart relationship with Him. It’s not a contract, but a covenant. To take the matter of interpreting how two people can live together into our own hands is, in reality, taking it out of His.
If you are living with someone currently, you need to go before the Lord and get your heart right with Him, then seek His guidance in setting things in order. Your options? Get married, unless of course the other person is a non-believer. If you both are professing believers, separate and then pray about marriage, or ignore what Scripture says. If you choose the latter, then you need to remove yourself from your local church because your sin will hurt others. If you are convicted, thank God for that, and follow through to bring forth the fruit of repentance. Seeking to please Jesus will bring forth fruit, and nothing pleases Him more than complete submission, which is proof of our love for Him.