CC Madhya 19.168
ānukūlye sarvendriye kṛṣṇānuśīlana
“A pure devotee must not cherish any desire other than to serve Kṛṣṇa. He should not offer worship to the demigods or to mundane personalities. He should not cultivate artificial knowledge, which is devoid of Kṛṣṇa consciousness, and he should not engage himself in anything other than Kṛṣṇa conscious activities. One must engage all one’s purified senses in the service of the Lord. This is the favorable execution of Kṛṣṇa conscious activities.