BRS 1.2.60 - 71
The execution and perfection of devotional service is not dependent on any material consideration.
Every other process of self-realization, however, is dependent on external circumstances. Jnana-yoga requires a peaceful, renounced disposition, and highly developed intellect. Astanga-yoga demands many rigid prerequisites that only a sannyasi can even begin to adopt. Karma-kanòa is also dependent on external circumstances — a yajna cannot be successful unless the time, place, and ingredients are flawless. Only bhakti-yoga is completely pure, free from any dependence on external prerequisites. That is why Srila Prabhupada titles the Fifth Chapter, "The Purity of Devotional Service."
Srila Rupa Gosvami mentions several common prerequisites for self-realization; such as good birth, purity, and proper execution of varnasrama-dharma.
He explains how bhakti is not dependent on them.
Birth
Although generally considered a disqualification from the path of self-realization, low birth does not impede the execution of devotional service.
Srila Prabhupada quotes Srimad-Bhagavatam (1.2.6) — devotional service has no material cause, and therefore “it cannot be checked by any material circumstances.
It is open for all, without any distinction, and it is the constitutional occupation of the living entities (pg 47).”
Srila Prabhupada then relates the interesting history of Srila Bhaktisiddhanta Sarasvati Thakura's opposition to the caste-gosvamis who claimed a birthright monopoly on pure devotional service. “There was a great hard struggle for some time, but it has turned out successfully, and it is now correctly and practically established that devotional service is not restricted to a particular class of men (pg 47).”
This point is particularly relevant to the International Society for Krsna Consciousness. Srila Prabhupada writes, “Our Krsna consciousness movement in the Western world is based on the above-mentioned proposition of Srila Bhaktisiddhanta Sarasvati Gosvami Prabhupada, our spiritual master. On his authority, we are claiming members from all sections of the Western countries. The so-called brahmanas claim that one who is not born into a brahmana family cannot receive the sacred thread and cannot become a high-grade Vaisnava. But we do not accept such a theory, because it is not supported by Rupa Gosvami nor by the strength of the various scriptures (pg 48).”
By quoting Padma Purana, Skanda Purana, and Hari-bhakti-vilasa, Srila Rupa Gosvami confirms that advancement and perfection in devotional service is equally open to all people, regardless of birth. (See pages 48 - 49)
Purity
Although a major pre-requisite for other processes of self-realization, purity is not a factor in determining one's eligibility to perform devotional service. Even if a devotee falls down from the standard of purity, he need not undergo any separate process of purification (prayascitta) such as karma or jnana. He can again take up devotional service immediately and be reinstated. One need not become purified before taking up devotional service. On the contrary, one becomes purified by taking up devotional service. (See page 49, first paragraph)
To validate this claim Srila Rupa Gosvami quotes Srimad-Bhagavatam (11.21.2), which says that the only qualification for beginning devotional service is to follow the principles given by the acarya, there is no need for any other method of purification.
Varnasrama-Dharma
Continuing the theme of bhakti's non-reliance upon purity, Srila Rupa Gosvami says that devotional service is not dependent on the proper execution of prescribed duties.
It is not entirely accurate to say that one must first become purified in varnasrama, and then concentrate on bhakti. Srila Rupa Gosvami cites many sastric evidences to confirm this.
Srimad-Bhagavatam (1.5.17): Narada Muni says, “Even if one does not execute his specific occupational duty, but immediately takes direct shelter of the lotus feet of Hari [Krsna], there will be no fault on his part, and in all circumstances his position is secure (pg 49).”11
Srimad-Bhagavatam (11.11.32): “My dear Uddhava, any person who takes shelter of Me in complete surrender and follows My instructions, giving up all occupational duties, is to be considered the first-class man (pg 50).”
Srimad-Bhagavatam (11.5.41): “My dear King, if someone gives up his occupational duties as they are prescribed for the different varnas and asramas, but takes complete shelter, surrendering himself unto the lotus feet of the Lord, such a person is no more a debtor... Nor has he any need to bother executing the five kinds of yajnas [sacrifices] for becoming free from sinful contamination. Simply by
11 Çréla Prabhupäda cites the Fifth Canto of Çrémad-Bhägavatam in his commentary on this text.
discharging devotional service, he is freed from all kinds of obligations (pgs 50 - 51)."12
Clearly, devotional service is not dependant on varnasrama-dharma. Simply by engaging in devotional service one will achieve all necessary purification. Thus, Srila Rupa Gosvami quotes Bhagavada-Gita (18.66): “Give up all your occupations and just become surrendered unto me. I give you assurance that I shall give you protection from all sinful reaction (pg 51).”
Srila Prabhupada emphasises the point, “Don't hesitate. Don't consider that because you are giving up all other engagements there will be some flaw in your life.
Don't think like that. I will give you all protection (pgs 51 - 52).”
If any doubt remains, Srila Rupa Gosvami quotes Agastya-samhita, and Srimad-Bhagavatam (11.5.42).
Conclusion
The conclusion is inspirational: bhakti-yoga is totally independent and self-sufficient;
no material impediment should discourage one from the path of surrender.
12 Çréla Prabhupäda's commentary comprises the rest of the paragraph and the next two paragraphs in The Nectar of Devotion.