Should Christians be associating with non-Christians? If Christians do not, the non-Christians will not hear, as in this passage:
For there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him. For whosoever shall call upon the name of the Lord shall be saved. How then shall they call on him in whom they have not believed? and how shall they believe in him of whom they have not heard? and how shall they hear without a preacher? And how shall they preach, except they be sent? as it is written, How beautiful are the feet of them that preach the gospel of peace, and bring glad tidings of good things! (Romans 10:12-15)
We Need to Associate with Unbelievers
And it came to pass, as Jesus sat at meat in the house, behold, many publicans and sinners came and sat down with him and his disciples. And when the Pharisees saw it, they said unto his disciples, Why eateth your Master with publicans and sinners? But when Jesus heard that, he said unto them, They that be whole need not a physician, but they that are sick. But go ye and learn what that meaneth, I will have mercy, and not sacrifice: for I am not come to call the righteous, but sinners to repentance. (Matthew 9:10-13)
And as he passed by, he saw Levi the son of Alphaeus sitting at the receipt of custom, and said unto him, Follow me. And he arose and followed him. And it came to pass, that, as Jesus sat at meat in his house, many publicans and sinners sat also together with Jesus and his disciples: for there were many, and they followed him. And when the scribes and Pharisees saw him eat with publicans and sinners, they said unto his disciples, How is it that he eateth and drinketh with publicans and sinners? When Jesus heard it, he saith unto them, They that are whole have no need of the physician, but they that are sick: I came not to call the righteous, but sinners to repentance. (Mark 2:14-17)
And after these things he went forth, and saw a publican, named Levi, sitting at the receipt of custom: and he said unto him, Follow me. And he left all, rose up, and followed him. And Levi made him a great feast in his own house: and there was a great company of publicans and of others that sat down with them. But their scribes and Pharisees murmured against his disciples, saying, Why do ye eat and drink with publicans and sinners? And Jesus answering said unto them, They that are whole need not a physician; but they that are sick. I came not to call the righteous, but sinners to repentance. (Luke 5:27-32)
And, behold, there was a man named Zacchaeus, which was the chief among the publicans, and he was rich. And he sought to see Jesus who he was; and could not for the press, because he was little of stature. And he ran before, and climbed up into a sycomore tree to see him: for he was to pass that way. And when Jesus came to the place, he looked up, and saw him, and said unto him, Zacchaeus, make haste, and come down; for to day I must abide at thy house. And he made haste, and came down, and received him joyfully. And when they saw it, they all murmured, saying, That he was gone to be guest with a man that is a sinner. And Zacchaeus stood, and said unto the Lord; Behold, Lord, the half of my goods I give to the poor; and if I have taken any thing from any man by false accusation, I restore him fourfold. And Jesus said unto him, This day is salvation come to this house, forsomuch as he also is a son of Abraham. For the Son of man is come to seek and to save that which was lost. (Luke 19:2-10)
God does not call Christians to avoid contact with the world. To the contrary, Christians should be making friends with lost people. Certainly, if Christians avoid associating with non-Christians, the unbelievers will not hear the gospel and its message of salvation. However, we do need to make sure that we are influencing the unbelievers and that they are not influencing us.
Associating with non-Christians has Limits!
We May Need to Eliminate Some Associations
And if thy right eye offend thee, pluck it out, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell. And if thy right hand offend thee, cut it off, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell. (Matthew 5:29-30)
Wherefore if thy hand or thy foot offend thee, cut them off, and cast them from thee: it is better for thee to enter into life halt or maimed, rather than having two hands or two feet to be cast into everlasting fire. And if thine eye offend thee, pluck it out, and cast it from thee: it is better for thee to enter into life with one eye, rather than having two eyes to be cast into hell fire. (Matthew 18:8-9)
And if thy hand offend thee, cut it off: it is better for thee to enter into life maimed, than having two hands to go into hell, into the fire that never shall be quenched: Where their worm dieth not, and the fire is not quenched. And if thy foot offend thee, cut it off: it is better for thee to enter halt into life, than having two feet to be cast into hell, into the fire that never shall be quenched: Where their worm dieth not, and the fire is not quenched. And if thine eye offend thee, pluck it out: it is better for thee to enter into the kingdom of God with one eye, than having two eyes to be cast into hell fire: Where their worm dieth not, and the fire is not quenched. (Mark 9:43-38)
Be not deceived: evil communications corrupt good manners. (1 Corinthians 15:33)
Examine yourselves, whether ye be in the faith; prove your own selves. Know ye not your own selves, how that Jesus Christ is in you, except ye be reprobates? (2 Corinthians 13:5)
End Bad Associations, Not Mutilate Ourselves!
A Christian May Need to Mature More Before Associating in Some Cases
These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into any city of the Samaritans enter ye not: But go rather to the lost sheep of the house of Israel. (Matthew 10:5-6)
After these things the Lord appointed other seventy also, and sent them two and two before his face into every city and place, whither he himself would come. (Luke 10:1)
In Matthew 10:5-6, the apostles were not very mature; and they were not ready to minister cross-culturally. Therefore, Jesus told them to stay in their own culture. However, in Luke 10:1, Jesus told the disciples to go to everybody.
If a Christian attempts a ministry that he is not mature enough for, this ministry will bear little or no fruit, or worse. For example, sending a Christian who is recovering from a drinking problem to minister in a bar district is risky.