If one uses the vibration of the holy name for the benefit of the material body, for material wealth and followers, or under the influence of greed or atheism — in other words, if one utters the name with offenses — such chanting will not produce the desired result very soon. Therefore one should diligently avoid offenses in chanting the holy name of the Lord.

From Srila Prabhupada’s translation of Cc Antya 3.60