In the Padma Purāṇa it is stated that even a person whose life is completely sinful will be completely protected by the Lord if he simply surrenders unto Him. So it is accepted that one who surrenders unto the Supreme Personality of Godhead becomes free from all sinful reactions. And even when a person becomes an offender unto the Supreme Personality of Godhead Himself, he can still be delivered simply by taking shelter of the holy names of the Lord: Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare. In other words, the chanting of Hare Kṛṣṇa is beneficial for eradicating all sins, but if one becomes an offender to the holy names of the Lord, then he has no chance of being delivered.
The offenses against the chanting of the holy name are as follows: (1) To blaspheme the devotees who have dedicated their lives for propagating the holy name of the Lord. (2) To consider the names of demigods like Lord Śiva or Lord Brahmā to be equal to, or independent of, the name of Lord Viṣṇu. (Sometimes the atheistic class of men take it that any demigod is as good as the Supreme Personality of Godhead, Viṣṇu. But one who is a devotee knows that no demigod, however great he may be, is independently as good as the Supreme Personality of Godhead. Therefore, if someone thinks that he can chant "Kālī, Kālī!" or "Durgā, Durgā!"and it is the same as Hare Kṛṣṇa, that is the greatest offense.) (3) To disobey the orders of the spiritual master. (4) To blaspheme the Vedic literature or literature in pursuance of the Vedic version. (5) To consider the glories of chanting Hare Kṛṣṇa to be imagination. (6) To give some interpretation on the holy name of the Lord. (7) To commit sinful activities on the strength of the holy name of the Lord. (It should not be taken that because by chanting the holy name of the Lord one can be freed from all kinds of sinful reaction, one may continue to act sinfully and after that chant Hare Kṛṣṇa to neutralize his sins. Such a dangerous mentality is very offensive and should be avoided.) (8) To consider the chanting of Hare Kṛṣṇa one of the auspicious ritualistic activities offered in the Vedas as fruitive activities (karma-kāṇḍa). (9) To instruct a faithless person about the glories of the holy name. (Anyone can take part in chanting the holy name of the Lord, but in the beginning one should not be instructed about the transcendental potency of the Lord. Those who are too sinful cannot appreciate the transcendental glories of the Lord, and therefore it is better not to instruct them in this matter.) (10) To not have complete faith in the chanting of the holy names and to maintain material attachments, even after understanding so many instructions on this matter.
Every devotee who claims to be a Vaiṣṇava must guard against these offenses in order to quickly achieve the desired success.