Srimad Bhagavatam Canto 02, Chapter 01, Text 22

SB 2.1.22

rajovaca
yatha sandharyate brahman
dharana yatra sammata
yadrsi va hared asu
purusasya mano-malam
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
The fortunate King Pariksit, inquiring further, said: O brahmana, please describe in full detail how and where the mind has to be applied and how the conception can be fixed so that the dirty things in a person’s mind can be removed.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
The dirty things in the heart of a conditioned soul are the root cause of all troubles for him. A conditioned soul is surrounded by the manifold miseries of material existence, but on account of his gross ignorance he is unable to remove the troubles due to dirty things in the heart, accumulated during the long prison life in the material world. He is actually meant to serve the will of the Supreme Lord, but on account of the dirty things in the heart, he likes to serve his concocted desires. These desires, instead of giving him any peace of mind, create new problems and thus bind him to the cycle of repeated birth and death. These dirty things of fruitive work and empiric philosophy can be removed only by association with the Supreme Lord. The Lord, being omnipotent, can offer His association by His inconceivable potencies. Thus persons who are unable to pin their faith on the personal feature of the Absolute are given a chance to associate with His virat-rupa, or the cosmic impersonal feature of the Lord. The cosmic impersonal feature of the Lord is a feature of His unlimited potencies. Since the potent and potencies are identical, even the conception of His impersonal cosmic feature helps the conditioned soul to associate with the Lord indirectly and thus gradually rise to the stage of personal contact.
 
Maharaja Pariksit was already directly connected with the personal feature of the Lord Sri Krsna, and as such he had no need to inquire from Sukadeva Gosvami about where and how to apply the mind in the impersonal virat-rupa of the Lord. But he inquired after a detailed description of the matter for the benefit of others, who are unable to conceive of the transcendental personal feature of the Lord as the form of eternity, knowledge and bliss. The nondevotee class of men cannot think of the personal feature of the Lord. Because of their poor fund of knowledge, the personal form of the Lord, like Rama or Krsna, is completely revolting to them. They have a poor estimation of the potency of the Lord. In the Bhagavad-gita (9.11) it is explained by the Lord Himself that people with a poor fund of knowledge deride the supreme personality of the Lord, taking Him to be a common man. Such men are ignorant of the inconceivable potency of the Lord. By the inconceivable potency of the Lord, He can move in human society or any other society of living beings and yet remain the same omnipotent Lord, without deviating in the slightest from His transcendental position. So, for the benefit of men who are unable to accept the Lord in His personal eternal form, Maharaja Pariksit inquired from Sukadeva Gosvami how to fix the mind on Him in the beginning, and the Gosvami replied in detail as follows.
Srimad Bhagavatam Canto 02, Chapter 01, Text 21
Srimad Bhagavatam Canto 02, Chapter 01, Text 23