Those who are not faithful in this devotional service cannot attain Me, O conqueror of enemies. Therefore they return to the path of birth and death in this material world.
The faithless cannot accomplish this process of devotional service; that is the purport of this verse. Faith is created by association with devotees. Unfortunate people, even after hearing all the evidence of Vedic literature from great personalities, still have no faith in God. They are hesitant and cannot stay fixed in the devotional service of the Lord. Thus faith is a most important factor for progress in Kṛṣṇa consciousness. In the Caitanya-caritāmṛta it is said that faith is the complete conviction that simply by serving the Supreme Lord, Śrī Kṛṣṇa, one can achieve all perfection. That is called real faith.
(Bhagavad-Gita----9:3----translation and purport).

These are the necessary qualifications of a prospective candidate who can expect to be elevated to the position of a pure unadulterated devotee. Such a candidate must always seek the association of pure devotees. One should not be misled by a pseudodevotee. He himself must be plain and gentle to receive the instructions of such a pure devotee. 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).

Pṛthā: Daughter of Mahārāja Śūrasena and sister of Vasudeva, Lord Kṛṣṇa's father. Later she was adopted by Mahārāja Kuntibhoja, and hence she is known as Kuntī. She is the incarnation of the success potency of the Personality of Godhead. The heavenly denizens from the upper planets used to visit the palace of King Kuntibhoja, and Kuntī was engaged for their reception. She also served the great mystic sage Durvāsā, and being satisfied by her faithful service, Durvāsā Muni gave her a mantra by which it was possible for her to call for any demigod she pleased. As a matter of inquisitiveness, she at once called for the sun-god, who desired couplement with her, but she declined. But the sun-god assured her immunity from virgin adulteration, and so she agreed to his proposal. As a result of this couplement, she became pregnant, and Karṇa was born by her. By the grace of the sun, she again turned into a virgin girl, but being afraid of her parents, she quitted the newly born child, Karṇa. After that, when she actually selected her own husband, she preferred Pāṇḍu to be her husband. Mahārāja Pāṇḍu later wanted to retire from family life and adopt the renounced order of life. Kuntī refused to allow her husband to adopt such life, but at last Mahārāja Pāṇḍu gave her permission to become a mother of sons by calling some other suitable personalities.
(Srimad Bhagavatam----1:13:3-4----purport).

As stated in Bhagavad-gītā (10.10), the Lord gives intelligence to the pure devotees so that they may be elevated to the highest perfectional stage. It is confirmed herein that a pure devotee, who constantly engages in the loving service of the Lord, is awarded all knowledge necessary to reach the Supreme Personality of Godhead. For such a devotee there is nothing valuable to be achieved but the Lord's service. If one serves faithfully, there is no possibility of frustration because the Lord Himself takes charge of the devotee's advancement. The Lord is seated in everyone's heart, and He knows the devotee's motive and arranges everything achievable. In other words, the pseudo devotee, who is anxious to achieve material gains, cannot attain the highest perfectional stage because the Lord is in knowledge of his motive. One merely has to become sincere in his purpose, and then the Lord is there to help in every way.
(Srimad Bhagavatam----3:13:49----purport).

The sages, the four Kumāras, now reject their cursing of the two doorkeepers, Jaya and Vijaya, because they are now conscious that persons who engage in the service of the Lord cannot be at fault at any stage. It is said that anyone who has implicit faith in the service of the Lord, or who actually engages in transcendental loving service, has all the good qualities of the demigods. Therefore, a devotee cannot be at fault. If sometimes it is found that he is in error by accident or by some temporary arrangement, that should not be taken very seriously. The cursing of Jaya and Vijaya is here repented. Now the Kumāras are thinking in terms of their position in the modes of passion and ignorance, and they are prepared to accept any kind of punishment from the Lord. In general, when dealing with devotees, we should not try to find faults. In Bhagavad-gītā also it is confirmed that the devotee who faithfully serves the Supreme Lord, even if found to commit a gross mistake, should be considered a sādhu, or saintly person. Due to former habits he may commit some wrong, but because he is engaged in the service of the Lord, that wrong should not be taken very seriously.
(Srimad Bhagavatam----3:16:25----purport).

One must be prepared to offer the necessary respect and honor to the spiritual master. He should not be unnecessarily envious of his Godbrothers. Rather, if a Godbrother is more enlightened and advanced in Kṛṣṇa consciousness, one should accept him as almost equal to the spiritual master, and one should be happy to see such Godbrothers advance in Kṛṣṇa consciousness. A devotee should always be very kind to the general public in instructing Kṛṣṇa consciousness because that is the only solution for getting out of the clutches of māyā. That is really humanitarian work, for it is the way to show mercy to other people who need it very badly. The word śuśrūṣābhiratāya indicates a person who faithfully engages in serving the spiritual master. One should give personal service and all kinds of comforts to the spiritual master. A devotee who does so is also a bona fide candidate for taking this instruction. The word bahir jāta-virāgāya means a person who has developed detachment from external and internal material propensities. Not only is he detached from activities which are not connected to Kṛṣṇa consciousness, but he should be internally averse to the material way of life.
(Srimad Bhagavatam----3:32:42----purport).

The dress and bodily features of the residents of Vaikuṇṭhaloka are properly described in these verses. The residents of Vaikuṇṭha, who are decorated with garlands and yellow silken garments, have four arms holding various weapons. Thus they conspicuously resemble Lord Viṣṇu. They have the same bodily features as Nārāyaṇa because they have attained the liberation of sārūpya, but they nevertheless act as servants. All the residents of Vaikuṇṭhaloka know perfectly well that their master is Nārāyaṇa, or Kṛṣṇa, and that they are all His servants. They are all self-realized souls who are nitya-mukta, everlastingly liberated. Although they could conceivably declare themselves Nārāyaṇa or Viṣṇu, they never do so; they always remain Kṛṣṇa conscious and serve the Lord faithfully. Such is the atmosphere of Vaikuṇṭhaloka. Similarly, one who learns the faithful service of Lord Kṛṣṇa through the Kṛṣṇa consciousness movement will always remain in Vaikuṇṭhaloka and have nothing to do with the material world.
(Srimad Bhagavatam----6:1:34-36----purport).