Eating With Sinners
In 1 Cor. 5:11 Paul writes "But now I have written unto you not to keep company, if any man that is called a brother be a fornicator, or covetous, or an idolater, or a railer, or a drunkard, or an extortioner; with such an one no not to eat." That sounds strange to me. What does he mean? Jesus eats with sinners, publicans and tax collectors. (Luke 15:1-2; Mark 2:15-16) What's the difference between eating in 1Cor. 5:11 and Jesus' eating?
You have to see that direction in the context of the chapter. There is church discipline case in view. A member of the congregation (a brother) is living a gross sin (vs. 1ff). Paul is directing the Corinth church to act Biblically. A person who lives in open fornication cannot be treated with the same privileges as another brother. We cannot maintain the same 'friendship level interaction' with such a person as if nothing is happening. Paul said that clearly in vs. 9, "I wrote unto you in an epistle not to company with fornicators." We are not to maintain a friendship relationship with sinners. Meals were and in some ways are privileges you share with friends. Yet he adds in vs. 10 that we should not carry this into the extreme. There are people you work with who are not Christians. They are thus not brothers or sisters. They may live worldly as fornicators. Can you share your lunch with them or have other types of association with them? Absolutely, for that is exactly what Jesus did also. The Lord Jesus didn't eat and drink with the publican and sinners because He approved of their lifestyle. He sought to evangelize them. So likewise Paul cautions not to stop that type of interaction in vs. 10, "Yet not altogether with the fornicators of this world, or with the covetous, or extortioners, or with idolaters; for them must ye needs go out of the world."
Paul finalizes to point out again (vs. 11) that with 'brothers who are living in sin' this approach should not be followed. They should not enjoy the privileges of friendship (though we always need to remain friendly) in order that this person may feel how much he is losing by living ungodly. Paul exhorted like this also in 2 Thess. 3:6 and 14-15.
Hopefully that answers your question.