And as Jesus passed forth from thence, he saw a man, named Matthew, sitting at the receipt of custom: and he saith unto him, Follow me. And he arose, and followed him. 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 9:9-13
In Scripture, we are taught to love our neighbor as ourselves and to care for and train disciples of Christ. But we are also taught to not have fellowship with those who desire to continue in sin and have no intention of following the Lord. In fact, we are warned that such behavior will actually hurt us rather than helping the other person.
Be not deceived: evil communications corrupt good manners.1st Corinthians 15:33
More often than not, the bad habits of others will change us for the worse rather our good behavior will influence them.
So, does this mean that we are to cease helping people who are living in sin? Certainly not! That is exactly what Jesus was doing with Matthew. He called him away from the sins of the publicans and was teaching him to be a disciple.
Our fellowship with those living in sin should continue as long as we are seeing signs of them turning away from the world and following Christ more. If we are making no progress, we should continue to pray for them but further fellowship could actually be harmful to our own discipleship.
Remember, Jesus ate with sinners, He did not SIN with sinners.