Although the holy name is non-different from the Lord, it is more powerful when heard from the lips of a pure devotee, because a pure devotee invokes the presence of the Lord by his pure chanting. Therefore, if we come in contact with the glorification of the Lord from the lips of His pure devotee, it can act upon our hearts. The Lord infuses the holy name with the potency to act upon the hearts of others. Thus if we even once hear the holy name of the Lord from a pure devotee of the Lord, we can be infused with a greater potency to chant, and our spiritual life can actually begin and progress.
(LFD, Vol2, Glories of the Holy Name, Pg 82, 4th paragraph)