A.T. Robertson Commentary 1 Corinthians 5:10

"not at all [meaning] with the fornicators of this world, or with the covetous and extortioners, or with idolaters; for then must ye needs go out of the world:" — 1 Corinthians 5:10 (ASV)

Not altogether (ου παντως). Not absolutely, not in all circumstances. Paul thus puts a limitation on his prohibition and confines it to members of the church. He has no jurisdiction over the outsiders (this world, του κοσμου τουτου).

The covetous (τοις πλεονεκταις). Old word for the over-reachers, those avaricious for more and more (πλεον, εχω, to have more). In N.T. only here, 6:10; Ephesians 5:5. It always comes in bad company (the licentious and the idolaters) like the modern gangsters who form a combination of liquor, lewdness, lawlessness for money and power.

Extortioners (αρπαξιν). An old adjective with only one gender, rapacious (Matthew 7:15; Luke 18:11), and as a substantive robber or extortioner . Bandits, hijackers, grafters they would be called today.

Idolaters (ειδωλολατραις). Late word for hirelings (λατρις) of the idols (ειδωλον), so our very word idolater. See 6:9; 10:7; Ephesians 5:5; Revelation 21:8; 22:15. Nageli regards this word as a Christian formation.

For then must ye needs (επε ωφειλετε ουν). This neat Greek idiom of επε with the imperfect indicative (ωφειλετε, from οφειλω, to be under obligation) is really the conclusion of a second-class condition with the condition unexpressed (Robertson, Grammar, p. 965). Sometimes αν is used also as in Heb 10:2, but with verbs of obligation or necessity αν is usually absent as here (cf. Hebrews 9:20). The unexpressed condition here would be, "if that were true" (including fornicators, the covetous, extortioners, idolaters of the outside world). Αρα means in that case.