1 Corinthians 5:10
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. 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.
In its setting the verse belongs to Paul's first letter confronting serious sexual misconduct at Corinth, which exposed the evils there and urged the church to act against members disgracing it by lascivious conduct before he arrived.
The command not to associate with fornicators, the covetous, extortioners, and idolaters applies to people inside the church who persist in such conduct, not to people outside the church.
It does not require avoiding all contact with sinners in the world, because that would require going out of the world or leaving the world.
Some believers twisted the statement about the world into an excuse for ignoring the required separation from immoral members.
As a rule for church discipline, offenders who pursue transgression are to be visited and labored with.
If they refuse to repent their names are not to be retained on the church books but they are to be separated from church fellowship, lest the saints be held accountable for their evil deeds.
Applied to daily life, the verse means Christians should not withdraw from the world or leave the world simply to avoid association with worldly people.
They should not make themselves odd and singular in dress merely to differ from worldly people, but may wear neat, plain, modest, and comfortable clothing even when worldly people dress the same way.