The word for holy, αγιος, implies being set apart and different from the world. But how different should Christians be? Let's look at a few verses about this and ask ourselves if we should be doing something different as individuals and as churches.
The first verse I want to look at is 2 John 10-11 which reads, "If there come any unto you, and bring not this doctrine, receive him not into your house, neither bid him God speed: For he that biddeth him God speed is partaker of his evil deeds."
In the verse and in the context this is specifically talking about people who would come into your house bringing a doctrine (or teaching) that is contrary to the doctrine of Christ. We should have nothing to do with these people. Note that this is not talking about unbelievers that desire to hear the gospel, but most commentators confine this instruction towards false-teachers.
Ephesians 5:11 And have no fellowship with the unfruitful works of darkness, but rather reprove them.
John Gill writes, "receive him not into house; neither into the house of God, suffer him not to preach there; nor into your own house, give him no entertainment there: false teachers always tried to creep into houses, where they served their own turn every way, both by feeding their bellies, and spreading their pernicious doctrines; and therefore such should: be avoided, both publicly and privately; their ministry should not be attended on in the church, or house of God; and they should not be entertained in private houses."
The Pulpit Commentaries provides further clarification: "But the reference plainly is to any one who wishes to come into the house to teach another doctrine, and to draw away the mother and the children from allegiance to their Lord."
There are plenty of false teachers out there today that I would never let into my house.
The next passage I want to look at is 1 Corinthians 5:9-11 "I wrote unto you in an epistle not to company with fornicators: Yet not altogether with the fornicators of this world, or with the covetous, or extortioners, or with idolaters; for then must ye needs go out of the world. 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 idolator, or a railer, or a drunkard, or an extortioner; with such an one no not to eat."
This is a more serious charge, that we should not even eat with someone who professes to be a brother in Christ, yet is continually sinning in the areas listed. As Christians, how well do we follow this? How serious are we about holding each other accountable and even telling someone we won't eat with them because of their sin?
Note that in these verses it is acknowledged that if we were to totally avoid fornicators that would be impossible unless we were to leave the world entirely.
However, it is permissible to eat with unbelievers. And in this verse and the ones before we see that it is preferable to eat with an unbeliever over a Christian who is following sin instead of Christ. God hates hypocrisy.
1 Corinthians 10:27 "If any of them that believe not bid you to a feast, and ye be disposed to go; whatsoever is set before you, eat, asking no question for conscience sake."
Finally, let's look at 2 Thessalonians 3, verse 6 and verses 14-15:
"Now we command you, brethren, in the name of our Lord Jesus Christ, that ye withdraw yourselves from every brother that walketh disorderly, and not after the tradition which he received of us."
"And if any man obey not our word by this epistle, note that man, and have no company with him, that he may be ashamed. Yet count him not as an enemy, but admonish him as a brother."
When Christians hold each other to such high standards, it first of all helps us to keep separate from the world. The more we act like the world and the more we tolerate, the less distinguishable we become. Secondly, this helps each other focus better on Christ. As people around us follow the Lord closely, it motivates us to follow Him as well.
Romans 16:17 Now I beseech you, brethren, mark them which cause divisions and offences contrary to the doctrine which ye have learned; and avoid them.