In this Age of Kali, the holy name of the Lord, the Hare Kṛṣṇa mahā-mantra, is the incarnation of Lord Kṛṣṇa. Simply by chanting the holy name, one associates with the Lord directly. Anyone who does this is certainly delivered.
To emphasize something to an ordinary person, one may repeat it three times, just as one might say, “You must do this! You must do this! You must do this!” Thus the Bṛhan-nāradīya Purāṇa repeatedly emphasizes the chanting of the holy name so that people may take it seriously and thus free themselves from the clutches of māyā. It is our practical experience in the Kṛṣṇa consciousness movement all over the world that many millions of people are factually coming to the spiritual stage of life simply by chanting the Hare Kṛṣṇa mahā-mantra regularly, according to the prescribed principles. Therefore our request to all our students is that they daily chant at least sixteen rounds of this harer nāma mahā-mantra offenselessly, following the regulative principles. Thus their success will be assured without a doubt.
Ref >> Srila Prabhupada Vani.