This confidential knowledge may never be explained to those who are not austere, or devoted, or engaged in devotional service, nor to one who is envious of Me. Persons who have not undergone the austerities of the religious process, who have never attempted devotional service in Kṛṣṇa consciousness, who have not tended a pure devotee, and especially those who are conscious of Kṛṣṇa only as a historical personality or who are envious of the greatness of Kṛṣṇa should not be told this most confidential part of knowledge.
(Bhagavad-Gita-------18:67-------purport).

There is no rigid fixture of time, and anyone can chant the holy name with attention and reverence at his convenience. The Lord is so kind to us that He can be present before us personally in the form of transcendental sound, but unfortunately we have no taste for hearing and glorifying the Lord's name and activities. We have already discussed developing a taste for hearing and chanting the holy sound. It is done through the medium of service to the pure devotee of the Lord.
(Srimad Bhagavatam-------1:2:17-------purport).

A pure devotee is a completely surrendered soul unto the Personality of Godhead. He knows the Personality of Godhead as the supreme proprietor and all others as His servitors. And by the association of pure devotees only, one can get rid of all sins accumulated by mundane association. A neophyte devotee must faithfully serve the pure devotee, and he should be very much obedient and strictly follow the instructions. These are the signs of a devotee who is determined to achieve success even in the existing duration of life.
(Srimad Bhagavatam-------1:5:29-------purport).

The Lord says in the Bhagavad-gītā that no one is dearer to Him than one who actually preaches the glories of the Lord to convert the nonbelievers and nondevotees. Such personalities as Nārada must be offered all due respects, like those offered to the Personality of Godhead Himself, and Mahārāja Yudhiṣṭhira, along with his noble brothers, were examples for others in receiving a pure devotee of the Lord like Nārada, who had no other business save and except singing the glories of the Lord along with his vīṇā, a musical stringed instrument.
(Srimad Bhagavatam-------1:13:38-------purport).

Actual knowledge of transcendental bliss can be bestowed upon anyone by a pure devotee. Vedeṣu durlabham adurlabham ātma-bhaktau [Bs. 5.33]. One cannot attain the perfection of spiritual life simply by following the directions of the Vedas. One has to approach a pure devotee: anyābhilāṣitā-śūnyaṁ jñāna-karmādy-anāvṛtam [Cc. Madhya 19.167]. By the grace of such a devotee, one can understand the Absolute Truth, Kṛṣṇa, and one's relationship with Him. A materialistic person sometimes thinks that simply by executing pious activities and remaining at home one can understand the Absolute Truth. That is denied in this verse. Nor can one understand the Absolute Truth simply by observing the rules and regulations of brahmacarya (celibacy). One only has to serve the pure devotee. That will help one understand the Absolute Truth without fail.
(Srimad Bhagavatam-------5:12:12-------purport).

One must render service to a Vaiṣṇava in order to get freed from sinful reactions, revive one's original Kṛṣṇa consciousness and be trained in how to love Kṛṣṇa. This is the result of mahātma-sevā. Of course, if one engages in the service of a pure devotee, the reactions of one's sinful life are vanquished automatically. Devotional service is necessary not to drive away an insignificant stock of sins, but to awaken our dormant love for Kṛṣṇa. As fog is vanquished at the first glimpse of sunlight, one's sinful reactions are automatically vanquished as soon as one begins serving a pure devotee; no separate endeavor is required.
(Srimad Bhagavatam-------6:1:16-------purport).

To save oneself, one must take shelter of a pure devotee. Narottama dāsa Ṭhākura therefore says, chāḍiyā vaiṣṇava-sevā nistāra pāyeche kebā. If one wants to save himself from material nature's onslaughts, which arise because of the material body, one must become Kṛṣṇa conscious and try to fully understand Kṛṣṇa. As stated in Bhagavad-gītā (4.9), janma karma ca me divyam evaṁ yo vetti tattvataḥ. One should understand Kṛṣṇa in truth, and this one can do only by serving a pure devotee. Thus Prahlāda Mahārāja prays that Lord Nṛsiṁhadeva place him in touch with a pure devotee and servant instead of awarding him material opulence. Every intelligent man within this material world must follow Prahlāda Mahārāja.
(Srimad Bhagavatam-------7:9:24-------purport).