1 Corinthians 5:10
1 Corinthians 5:1010I was not including the sexually immoral of this world, or the greedy and swindlers, or idolaters. In that case you would have to leave this world.
JWs cite 1 Cor 5 selectively — verses 11 and 13 (about removing the wicked person from among you) are central to the disfellowshipping framework — but verse 10 itself is rarely surfaced in Watchtower publications because it qualifies the preceding verse in a way that pushes back against categorical separation from outsiders. Where v.10 does appear, it tends to be framed as a reluctant concession that some contact with worldly people is unavoidable.
Paul is unusually explicit here. He clarifies that his earlier command not to associate with sexually immoral people did not mean "with the sexually immoral people of this world or the greedy and swindlers, or with idolaters, since then you would need to go out of the world." The "world" he refers to is the ordinary social fabric outside the church — neighbours, customers, family. Paul's restriction in v.11 applies to people inside the congregation calling themselves brothers; v.10 names what the rule does not cover. The categorical Watchtower reading of "bad associations" (1 Cor 15:33) collapses against Paul's own qualification here: avoiding all non-Christian sinners would require leaving the world entirely, and Paul says clearly that is not what he means.