There are two different passages in the New Testament, both in Pauline epistles, in which *greed* is seemingly equated with *idolatry*. Since the way in which the phrases are translated can affect their meaning, as it applies to this particular context, I'll quote them each in several different versions: ---------- Col 3:5 ------- [NASB][1] > Therefore consider the members of your earthly body as dead to immorality, impurity, passion, evil desire, and greed, which amounts to idolatry. [ESV][2] > Put to death therefore what is earthly in you: sexual immorality, impurity, passion, evil desire, and covetousness, which is idolatry. [NIV][3] > Put to death, therefore, whatever belongs to your earthly nature: sexual immorality, impurity, lust, evil desires and greed, which is idolatry. [NKJV][4] > Therefore put to death your members which are on the earth: fornication, uncleanness, passion, evil desire, and covetousness, which is idolatry. ---------- Eph 5:5 ------- [NASB][5] > For this you know with certainty, that no immoral or impure person or covetous man, who is an idolater, has an inheritance in the kingdom of Christ and God. [ESV][6] > For you may be sure of this, that everyone who is sexually immoral or impure, or who is covetous (that is, an idolater), has no inheritance in the kingdom of Christ and God. [NIV][7] > For of this you can be sure: No immoral, impure or greedy person—such a person is an idolater—has any inheritance in the kingdom of Christ and of God. [NKJV][8] > For this you know, that no fornicator, unclean person, nor covetous man, who is an idolater, has any inheritance in the kingdom of Christ and God. ---------- Given these two passages, it seems likely that the Apostle Paul regularly taught that greed and covetousness were a form of idolatry. Since he, unfortunately, gives no further explanation for why he equates the two, we can assume that either his teaching on the matter was already well known by the audiences, or he felt that the reason for the deduction should be obvious to any audience. If his reasoning for the deduction was well known at the time, that is no longer the case today, so either way we are left with the task of surmising the reason. It is not a terribly difficult problem to solve. Idolatry is wrong because you are worshiping, loving, and giving devotion to some object rather than to God. Greed is also wrong because you are loving and giving devotion to some object rather than what God has already provided for you. Once that Biblical reasoning is established, the reasoning you cited, as being popular among evangelicals, is not difficult to justify. [1]: https://www.biblegateway.com/passage/?search=Col%203%3A5&version=NASB [2]: https://www.biblegateway.com/passage/?search=Col%203%3A5&version=ESV [3]: https://www.biblegateway.com/passage/?search=Col%203%3A5&version=NIV [4]: https://www.biblegateway.com/passage/?search=Col%203%3A5&version=NKJV [5]: https://www.biblegateway.com/passage/?search=Eph%205%3A5&version=NASB [6]: https://www.biblegateway.com/passage/?search=Eph%205%3A5&version=ESV [7]: https://www.biblegateway.com/passage/?search=Eph%205%3A5&version=NIV [8]: https://www.biblegateway.com/passage/?search=Eph%205%3A5&version=NKJV