Srimad Bhagavatam Canto 06, Chapter 01, Text 16

SB 6.1.16

na tatha hy aghavan rajan
 puyeta tapa-adibhih
yatha krsnarpita-pranas
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
My dear King, if a sinful person engages in the service of a bona fide devotee of the Lord and thus learns how to dedicate his life unto the lotus feet of Krsna, he can be completely purified. One cannot be purified merely by undergoing austerity, penance, brahmacarya and the other methods of atonement I have previously described.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Tat-purusa refers to a preacher of Krsna consciousness, such as the spiritual master. Srila Narottama dasa Thakura has said, chadiya vaisnava-seva nistara payeche keba: “Without serving a bona fide spiritual master, an ideal Vaisnava, who can be delivered from the clutches of maya?” This idea is also expressed in many other places. Srimad-Bhagavatam (5.5.2) says, mahat-sevam dvaram ahur vimukteh: if one desires liberation from the clutches of maya, one must associate with a pure devotee mahatma. A mahatma is one who engages twenty-four hours daily in the loving service of the Lord. As Krsna says in Bhagavad-gita (9.13):
mahatmanas tu mam partha
 daivim prakrtim asritah
bhajanty ananya-manaso
 jñatva bhutadim avyayam
“O son of Prtha, those who are not deluded, the great souls, are under the protection of the divine nature. They are fully engaged in devotional service because they know Me as the Supreme Personality of Godhead, original and inexhaustible.” Thus the symptom of a mahatma is that he has no engagement other than service to Krsna. One must render service to a Vaisnava in order to get freed from sinful reactions, revive one’s original Krsna consciousness and be trained in how to love Krsna. This is the result of mahatma-seva. 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 Krsna. 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.
The word krsna-arpita-pranah refers to a devotee who dedicates his life to serving Krsna, not to being saved from the path to hellish life. A devotee is narayana-parayana, or vasudeva-parayana, which means that the path of Vasudeva, or the devotional path, is his life and soul. Narayana-parah sarve na kutascana bibhyati (Bhag. 6.17.28): such a devotee is not afraid of going anywhere. There is a path toward liberation in the higher planetary systems and a path toward the hellish planets, but a narayana-para devotee is unafraid wherever he is sent; he simply wants to remember Krsna, wherever he may be. Such a devotee is unconcerned with hell and heaven; he is simply attached to rendering service to Krsna. When a devotee is put into hellish conditions, he accepts them as Krsna’s mercy: tat te ’nukampam susamiksamanah (Bhag. 10.14.8). He does not protest, “Oh, I am such a great devotee of Krsna. Why have I been put into this misery?” Instead he thinks, “This is Krsna’s mercy.” Such an attitude is possible for a devotee who engages in the service of Krsna’s representative. This is the secret of success.
Srimad Bhagavatam Canto 06, Chapter 01, Text 15
Srimad Bhagavatam Canto 06, Chapter 01, Text 17