Why does Paul call greed the same as idolatry?

Paul makes a stark equation in Ephesians 5:5. He doesn't say the greedy person is like an idolater, or acts as if they worship an idol. He says:

"For know this with certainty: every sexually immoral person or impure person or covetous person — who is an idolater — has no inheritance in the kingdom of Christ and God." — Ephesians 5:5

The relative clause is a predicate nominative of identity — the Greek verb estin (ἐστιν) declares what the person is, not what they resemble. The covetous person is an idolater.

The logic becomes clear once you look at the word. Eidōlolatrēs (G1496) is a transparent compound: eidōlon (εἴδωλον, G1497, "image, idol") + latreuō (λατρεύω, G3000, "to serve, worship"). An idolater is someone who gives worship-level devotion to something that is not God. And pleonektēs (πλεονέκτης, G4123) means literally "one who wants to have more" — the person whose craving for material gain has become the driving center of their life. That craving has displaced God. The functional center has shifted. That is exactly what idolatry is.

This pairing of greed and idolatry is not Paul's innovation — the prophets established it. Hosea's entire book is built on the metaphor that Israel's idolatry is spiritual adultery (Hosea 1–3). Ezekiel 16 and 23 depict Jerusalem and Samaria as unfaithful wives who prostituted themselves to foreign nations and their gods. The connection between sexual sin and idolatry runs deep in the prophetic tradition because they are both forms of the same fundamental betrayal: giving to something else the exclusive devotion that belongs to God.

In 1 Corinthians 6:9–10, in Revelation 21:8, in Revelation 22:15 — every time the New Testament lists those who will not inherit the kingdom, these two categories appear together. They are the two fundamental covenant-breaking categories: infidelity to God and infidelity in the body. Paul is not innovating. He is standing in a long tradition. For the full analysis of every exclusion list in the New Testament, see Who Will Not Inherit the Kingdom.