There are ten offenses to avoid in chanting the Hare Kṛṣṇa mahā-mantra. The first offense is to blaspheme great personalities who are engaged in distributing the holy name of the Lord. It is said in the śāstra (CC.3:7:11, kṛṣṇa-śakti vinā nahe tāra pravartana: one cannot distribute the holy names of the Hare Kṛṣṇa mahā-mantra unless he is empowered by the Supreme Personality of Godhead. Therefore one should not criticize or blaspheme a devotee who is thus engaged.
(Sri Caitanya Caritamrta------1:8:24-------purport).

This is a confirmation of the statement kṛṣṇa-śakti vinā nahe tāra pravartana. Unless one is specifically empowered by the Supreme Personality of Godhead, he cannot spread the Kṛṣṇa consciousness movement. An empowered devotee sees and feels himself to be the lowest of men, for he knows that whatever he does is due to the inspiration given by the Lord in the heart. This is confirmed by Lord Kṛṣṇa in the Bhagavad-gītā (10.10):

teṣāṁ satata-yuktānāṁ bhajatāṁ prīti-pūrvakam
dadāmi buddhi-yogaṁ taṁ yena mām upayānti te
"To those who are constantly devoted to serving Me with love, I give the understanding by which they can come to Me."

(Sri Caitanya Caritamrta------2:19:135-------purport).

Parāsya śaktir vividhaiva śrūyate (Cc. Madhya 13.65, purport). The Supreme Lord has multipotencies, which the Lord bestows on His fortunate devotees. The Lord has a special potency by which He spreads the Kṛṣṇa consciousness movement. This is explained in the Caitanya-caritāmṛta (CC.3:7:11): kali-kālera dharma—kṛṣṇa-nāma-saṅkīrtana/ kṛṣṇa-śakti vinā nahe tāra pravartana. "One cannot spread the holy name of Kṛṣṇa without being specifically empowered by Lord Kṛṣṇa." A devotee who receives this power from the Lord must be considered very fortunate. The Kṛṣṇa consciousness movement is spreading to enlighten people about their real position, their original relationship with Kṛṣṇa. One requires Kṛṣṇa's special power in order to be able to do this. People forget their relationship with Kṛṣṇa and work under the spell of māyā life after life, transmigrating from one body to another. This is the process of material existence. The Supreme Lord Śrī Kṛṣṇa personally descends to teach people that their position in the material world is a mistaken one. The Lord again comes as Śrī Caitanya Mahāprabhu to induce people to take to Kṛṣṇa consciousness. The Lord also empowers a special devotee to teach people their constitutional position.
(Sri Caitanya Caritamrta------2:19:114-------purport).

To describe Śrī Caitanya Mahāprabhu or Lord Śrī Kṛṣṇa, one needs supernatural power, which is the grace and mercy of the Lord. Without this grace and mercy, one cannot compose transcendental literature. By dint of the grace of the Lord, however, even one who is unfit for a literary career can describe wonderful transcendental topics. Description of Kṛṣṇa is possible for one who is empowered. Kṛṣṇa-śakti vinā nahe tāra pravartana (CC.3:7:11). Unless endowed with the mercy of the Lord, one cannot preach of the Lord's name, fame, qualities, form, entourage and so on. It should be concluded, therefore, that the writing of Śrī Caitanya-caritāmṛta by Kṛṣṇadāsa Kavirāja Gosvāmī manifests specific mercy bestowed upon the author, although he thought of himself as the most fallen. We should not consider him fallen because he describes himself as such. Rather, anyone who is able to compose such transcendental literature is our esteemed master.
(Sri Caitanya Caritamrta------3:13:1-------purport).

Formerly, all activities were performed in connection with Viṣṇu, but after Satya-yuga there were symptoms of disrespectful dealings among Vaiṣṇavas. Śrīla Bhaktivinoda Ṭhākura has said that a Vaiṣṇava is he who has helped others become Vaiṣṇavas. An example of one who has converted many others into Vaiṣṇavas is Nārada Muni. A powerful Vaiṣṇava who has converted others into Vaiṣṇavas is to be worshiped, but because of material contamination, sometimes such an exalted Vaiṣṇava is disrespected by other, minor Vaiṣṇavas. When great saintly persons saw this contamination, they introduced worship of the Deity in the temple. This began in Tretā-yuga and was especially prominent in Dvāpara-yuga (dvāpare paricaryāyāṁ). But in Kali-yuga, worship of the Deity is being neglected. Therefore chanting of the Hare Kṛṣṇa mantra is more powerful than Deity worship. Śrī Caitanya Mahāprabhu set a practical example in that He did not establish any temples or Deities, but He profusely introduced the saṅkīrtana movement. Therefore Kṛṣṇa consciousness preachers should give more stress to the saṅkīrtana movement, especially by distributing transcendental literature more and more. This helps the saṅkīrtana movement. Whenever there is a possibility to worship the Deity, we may establish many centers, but generally we should give more stress to the distribution of transcendental literature, for this will be more effective in converting people to Kṛṣṇa consciousness.
It is said in Śrīmad-Bhāgavatam (11.2.47):

arcāyām eva haraye
pūjāṁ yaḥ śraddhayehate
na tad-bhakteṣu cānyeṣu
sa bhaktaḥ prākṛtaḥ smṛtaḥ
"A person who is very faithfully engaged in the worship of the Deity in the temple but does not know how to behave toward devotees or people in general is called a prākṛta-bhakta, or kaniṣṭha-adhikārī." A prākṛta devotee, or neophyte devotee, is still on the material platform. He certainly engages in worshiping the Deity, but he cannot appreciate the activities of a pure devotee. It has actually been seen that even an authorized devotee who is engaged in the service of the Lord by preaching the mission of Kṛṣṇa consciousness is sometimes criticized by neophyte devotees. Such neophytes are described by Viśvanātha Cakravartī Ṭhākura: sarva-prāṇi-sammānanāsamarthānām avajñā spardhādimatāṁ tu bhagavat-pratimaiva pātram ity āha. For those who cannot properly appreciate the activities of authorized devotees, Deity worship is the only way for spiritual advancement. In the Caitanya-caritāmṛta (CC.3:7:11) it is clearly said, kṛṣṇa-śakti vinā nahe tāra pravartana: without being authorized by Kṛṣṇa, one cannot preach the holy name of the Lord throughout the entire world. Nevertheless, a devotee who does so is criticized by neophyte devotees, kaniṣṭha-adhikārīs, who are on the lower stages of devotional service. For them, Deity worship is strongly recommended.

(Srimad Bhagavatam-------7:14:39-------purport).

According to the Caitanya-caritāmṛta (Antya-līlā 7.11), kṛṣṇa-śakti vinā nahe tāra pravartana. An authorized spiritual master empowered by Kṛṣṇa can spread the glories of the holy name of the Lord, for he has power of attorney from the Supreme Personality of Godhead. In the mundane world, anyone possessing his master's power of attorney can act on behalf of his master. Similarly, a spiritual master empowered by Kṛṣṇa through his own bona fide spiritual master should be considered as good as the Supreme Personality of Godhead Himself. That is the meaning of sākṣād-dharitvena. Śrī Caitanya Mahāprabhu therefore describes the activities of the Supreme Personality of Godhead and the bona fide spiritual master as follows.

(Sri Caitanya Caritamrta------2:10:136-------purport).

Many fools, not knowing the transcendental nature of the Hare Kṛṣṇa mahā-mantra, sometimes impede our loudly chanting this mantra, yet one who is actually advanced in the fulfillment of chanting the Hare Kṛṣṇa mahā-mantra induces others to chant also. Kṛṣṇadāsa Kavirāja Gosvāmī explains, kṛṣṇa-śakti vinā nahe tāra pravartana: unless one receives special power of attorney from the Supreme Personality of Godhead, he cannot preach the glories of the Hare Kṛṣṇa mahā-mantra. As devotees propagate the Hare Kṛṣṇa mahā-mantra, the general population of the entire world gets the opportunity to understand the glories of the holy name. While chanting and dancing or hearing the holy name of the Lord, one automatically remembers the Supreme Personality of Godhead, and because there is no difference between the holy name and Kṛṣṇa, the chanter is immediately linked with Kṛṣṇa. Thus connected, a devotee develops his original attitude of service to the Lord. In this attitude of constantly serving Kṛṣṇa, which is called bhāva, he always thinks of Kṛṣṇa in many different ways. One who has attained this bhāva stage is no longer under the clutches of the illusory energy. When other spiritual ingredients, such as trembling, perspiration and tears, are added to this bhāva stage, the devotee gradually attains love of Kṛṣṇa.
The holy name of Kṛṣṇa is called the mahā-mantra. Other mantras mentioned in the Nārada Pañcarātra are known simply as mantras, but the chanting of the holy name of the Lord is called the mahā-mantra.

(Sri Caitanya Caritamrta------1:7:83-------purport).

If one saw the personal characteristics and activities of Śrī Caitanya Mahāprabhu, one would certainly be convinced that He was the Supreme Personality of Godhead. One can ascertain this by following in the footsteps of the śāstric injunctions. This sincere study and appreciation of Śrī Caitanya Mahāprabhu is also applicable to His authorized devotees, and it is clearly stated in the Caitanya-caritāmṛta (Antya-līlā 7.11):

kali-kālera dharma—kṛṣṇa-nāma-saṅkīrtana
kṛṣṇa-śakti vinā nāhe tāra pravartana
In this Age of Kali, real religious propaganda should induce people to chant the Hare Kṛṣṇa mahā-mantra. This is possible for someone who is especially empowered by Kṛṣṇa. No one can do this without being especially favored by Kṛṣṇa.

(Sri Caitanya Caritamrta------2:25:9-------purport).