Srimad Bhagavatam 3.32.23
janayaty āśu vairāgyaḿ
jñānaḿ yad brahma-darśanam
Engagement in Kṛṣṇa consciousness and application of devotional service unto Kṛṣṇa make it possible to advance in knowledge and detachment, as well as in self-realization.
It is said by less intelligent men that bhakti-yoga, or devotional service, is meant for persons who are not advanced in transcendental knowledge and renunciation. But the fact is that if one engages in the devotional service of the Lord in full Kṛṣṇa consciousness, he does not have to attempt separately to practice detachment or to wait for an awakening of transcendental knowledge. It is said that one who engages unflinchingly in the devotional service of the Lord actually has all the good qualities of the demigods develop in him automatically. One cannot discover how such good qualities develop in the body of a devotee, but actually it happens. There is one instance where a hunter was taking pleasure in killing animals, but after becoming a devotee he was not prepared to kill even an ant. Such is the quality of a devotee.
Those who are very eager to advance in transcendental knowledge can engage themselves in pure devotional service, without wasting time in mental speculation. For arriving at the positive conclusions of knowledge in the Absolute Truth, the word brahma-darśanam is significant in this verse. Brahma-darśanam means to realize or to understand the Transcendence. One who engages in the service of Vāsudeva can actually realize what Brahman is. If Brahman is impersonal, then there is no question of darśanam, which means "seeing face to face." Darśanam refers to seeing the Supreme Personality of Godhead, Vāsudeva. Unless the seer and the seen are persons, there is no darśanam. Brahma-darśanam means that as soon as one sees the Supreme Personality of Godhead, he can at once realize what impersonal Brahman is.
A devotee does not need to make separate investigations to understand the nature of Brahman. Bhagavad-gītā also confirms this. Brahma-bhūyāya kalpate: a devotee at once becomes a self-realized soul in the Absolute Truth.