Srimad Bhagavatam Canto 11, Chapter 17, Text 36

SB 11.17.36

evam brhad-vrata-dharo
 brahmano ’gnir iva jvalan
mad-bhaktas tivra-tapasa
 dagdha-karmasayo ’malah
A brahmana observing the great vow of celibacy becomes brilliant like fire and by serious austerity burns to ashes the propensity to perform material activities. Free from the contamination of material desire, he becomes My devotee.
The process of liberation is described in this verse. Once when Srila Prabhupada was traveling by airplane, a fellow passenger, who happened to be a priest, told him that he had seen his disciples and found them “bright-faced.” Srila Prabhupada was fond of relating this incident. The spirit soul is more brilliant than the sun, and as the process of spiritual purification gradually takes effect, even the external form of a devotee becomes effulgent. The glowing fire of spiritual knowledge burns to ashes the mentality of sense gratification, and one naturally becomes austere and disinterested in mundane enjoyment. Among all austerities, the best is celibacy, by which the shackles of material life immediately become slackened. One who is amala, free from material desire, is known as a pure devotee of the Lord. On the paths of jñana, karma and yoga the mind retains the concept of personal interest, but on the path of pure devotion the mind is trained to see only the interests of the Personality of Godhead. Thus a pure devotee of the Lord is amala, completely pure.
Srimad Bhagavatam Canto 11, Chapter 17, Text 34-35
Srimad Bhagavatam Canto 11, Chapter 17, Text 37