Srimad Bhagavatam Canto 05, Chapter 01, Text 05

SB 5.1.5

sri-suka uvaca
badham uktam bhagavata uttamaslokasya
srimac-caranaravinda-makaranda-rasa avesita-cetaso
bhagavata-paramahamsa-dayita-katham kiñcid
antaraya-vihatam svam sivatamam padavim na prayena hinvanti.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Sri Sukadeva Gosvami said: What you have said is correct. The glories of the Supreme Personality of Godhead, who is praised in eloquent, transcendental verses by such exalted personalities as Brahma, are very pleasing to great devotees and liberated persons. One who is attached to the nectarean honey of the Lord’s lotus feet, and whose mind is always absorbed in His glories, may sometimes be checked by some impediment, but he still never gives up the exalted position he has acquired.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Sri Sukadeva Gosvami accepted both of the King’s propositions — that a person who is advanced in Krsna consciousness cannot embrace materialistic life again and that one who has embraced materialistic life cannot take up Krsna consciousness at any stage of his existence. Although accepting both these statements, Sukadeva Gosvami qualified them by saying that a person who has once absorbed his mind in the glories of the Supreme Personality of Godhead may sometimes be influenced by impediments but he still does not give up his exalted devotional position.
According to Srila Visvanatha Cakravarti Thakura, there are two kinds of impediments to devotional service. The first is an offense at the lotus feet of a Vaisnava. This is called vaisnava-aparadha. Sri Caitanya Mahaprabhu warned His devotees not to commit vaisnava-aparadha, which He described as the mad elephant offense. When a mad elephant enters a beautiful garden, it destroys everything, leaving a barren field. Similarly, the power of vaisnava-aparadha is so great that even an advanced devotee becomes almost devoid of his spiritual assets if he commits it. Since Krsna consciousness is eternal, it cannot be destroyed altogether, but advancement may be checked for the time being. Thus vaisnava-aparadha is one kind of impediment to devotional service. Sometimes, however, the Supreme Personality of Godhead or His devotee desires to impede one’s devotional service. For example, Hiranyakasipu and Hiranyaksa were formerly Jaya and Vijaya, the gatekeepers in Vaikuntha, but by the desire of the Lord they became His enemies for three lives. Thus the desire of the Lord is another kind of impediment. But in both cases, the pure devotee, once advanced in Krsna consciousness, cannot be lost. Following the orders of his superiors (Svayambhuva and Lord Brahma), Priyavrata accepted family life, but this did not mean he lost his position in devotional service. Krsna consciousness is perfect and eternal, and therefore it cannot be lost under any circumstances. Because the material world is full of obstructions to advancement in Krsna consciousness, there may appear to be many impediments, yet Krsna, the Supreme Personality of Godhead, declares in Bhagavad-gita (9.31), kaunteya pratijanihi na me bhaktah pranasyati: once one has taken shelter at the lotus feet of the Lord, he cannot be lost.
In this verse, the word sivatamam is very significant. Sivatamam means “the most auspicious.” The devotional path is so auspicious that a devotee cannot be lost under any circumstances. This is described in the Srimad Bhagavad-gita by the Lord Himself. Partha naiveha namutra vinasas tasya vidyate: “My dear Arjuna, for a devotee there is no question of being lost, either in this life or in the next.” (Bg. 6.40) In Bhagavad-gita (6.43) the Lord clearly explains how this is so.
tatra tam buddhi-samyogam
 labhate paurva-dehikam
yatate ca tato bhuyah
 samsiddhau kuru-nandana
By the order of the Lord, a perfect devotee sometimes comes to this material world like an ordinary human being. Because of his previous practice, such a perfect devotee naturally becomes attached to devotional service, apparently without cause. Despite all kinds of impediments due to surrounding circumstances, he automatically perseveres in devotional service and gradually advances until he once again becomes perfect. Bilvamangala Thakura had been an advanced devotee in his previous life, but in his next life he became greatly fallen and was attached to a prostitute. Suddenly, however, his entire behavior was changed by the words of the very prostitute who had so much attracted him, and he became a great devotee. In the lives of exalted devotees, there are many such instances, proving that once one has taken to the shelter of the lotus feet of the Lord he cannot be lost (kaunteya pratijanihi na me bhaktah pranasyati).
The fact is, however, that one becomes a devotee when he is completely freed from all reactions to sinful life. As Krsna states in Bhagavad-gita (7.28):
yesam tv anta-gatam papam
 jananam punya-karmanam
te dvanda-moha-nirmukta
 bhajante mam drdha-vratah
“Persons who have acted piously in previous lives and in this life, whose sinful actions are completely eradicated and who are freed from the duality of illusion engage themselves in My service with determination.” On the other hand, as Prahlada Maharaja said:
matir na krsne paratah svato va
 mitho ’bhipadyeta grha-vratanam
A person who is too attached to materialistic family life — home, family, wife, children and so on — cannot develop Krsna consciousness.
These apparent contradictions are resolved in the life of a devotee by the grace of the Supreme Lord, and therefore a devotee is never bereft of his position on the path of liberation, which is described in this verse as sivatamam padavim.
Srimad Bhagavatam Canto 05, Chapter 01, Text 04
Srimad Bhagavatam Canto 05, Chapter 01, Text 06