1 Corinthians 5:11 says, “But now I have written to you not to keep company with anyone NAMED A BROTHER, who is sexually immoral, or covetous, or an idolater, or a reviler, or a drunkard, or an extortioner—not even to eat with such a person.” In this chapter, the apostle Paul was speaking to the local church at Corinth. Verse 1 reads, “It is actually reported that there is sexual immorality AMONG YOU, and such sexual immorality as is not even named among the Gentiles—that a man has his father’s wife.” This man was guilty of a gross sin and yet he was still allowed to be in fellowship in that local church. It is clear he was still in fellowship because Paul said he was AMONG YOU. In verse 2 Paul rebukes them for be “puffed up” (proud) instead of “mourning and putting the man, who was a professing Christ, out of fellowship.” In the remainder of the chapter Paul calls upon them to have a special meeting for the discipline of this offender whereby he would be officially removed from fellowship. This is brought out clearly in verses 4-5, “In the name of our Lord Jesus Christ, when you are gathered together, along with my spirit, with the power of the Lord Jesus Christ, deliver such a one to Satan for the destruction of the flesh, that his spirit may be saved in the day of the Lord Jesus.” When the Lord Jesus was here on earth, He gave believers in a local church the authority to do this (please read Matthew 18:15-20). As we see in that passage, the Lord Himself promises to be “in the midst” of the church when this action is taken (verse 20) and heaven itself sanctions this act of discipline (verse 18).

Verse 11 goes a step further, for believers are told “not to keep company with ANYONE NAMED A BROTHER…not even to eat with such a person.” This means we should also avoid that person SOCIALLY, including not sitting down to eat with them. Again, this was a man who professed to know Christ as his Savior and this profession linked him with Christ and his sin dishonored Christ and was defiling the local church. This demanded complete separation from him (collectively in a church setting or individually in a social setting). The world would be looking at him as “an evil person” and thus Paul ends the chapter with these words, “Therefore ‘put away from yourselves the evil person’” (verse 13).

Why did I go into such detail explaining the contents of this chapter? I wanted to show you that verse 11, along with the whole chapter, is instruction for a local church in dealing with “anyone named a BROTHER” who is living in sin. It is not instruction for what a Christian should do with an UNBELIEVING SPOUSE. I assume, from your question, that your spouse is living in some kind of sin (perhaps one mentioned in verse 11) and that you thought the instruction here may be applicable to you which means you couldn’t keep company with your spouse. But verses 9-10 make it clear that Paul is NOT speaking of a believer’s contact with unbelievers. Those verses say, “I wrote to you in my epistle not to keep company with sexually immoral people. Yet I certainly DID NOT MEAN THAT SEXUALLY IMMORAL PEOPLE OF THIS WORLD.” Here is what William MacDonald (a Christian commentator) said about those verses: “He did not mean to imply that they should separate themselves from any contact at all with ungodly men. As long as we are in the world, it is necessary for us to do business with unsaved people and we have no way of knowing the depths of sin to which they have descended. In order to live a life of complete isolation from sinners, YOU WOULD NEED TO GO OUT OF THE WORLD.”

Regarding you two being “one flesh,” when God instituted marriage in the Garden of Eden He said, “Therefore a man shall leave his father and mother and be joined to his wife, and THEY SHALL BECOME ONE FLESH.” The Lord Jesus reaffirmed this in Matthew 19:5 and added the words, “So then, they are no longer two but one flesh. Therefore, what God has joined together, let not man separate” (verse 6). God Himself has formed what should be a lifelong UNITY and no one should separate the two.  (DO)  (665.3)