SB 7.7.17

bhavatām api bhūyān me
 yadi śraddadhate vacaḥ
vaiśāradī dhīḥ śraddhātaḥ
 strī-bālānāṁ ca me yathā
Word for word: 
bhavatām — of yourselves; api — also; bhūyāt — it may be; me — of me; yadi — if; śraddadhate — you believe in; vacaḥ — the words; vaiśāradī — of the most expert, or in relation with the Supreme Lord; dhīḥ — intelligence; śraddhātaḥ — because of firm faith; strī — of women; bālānām — of small boys; ca — also; me — of me; yathā — just as.
Translation: 
Prahlāda Mahārāja continued: My dear friends, if you can place your faith in my words, simply by that faith you can also understand transcendental knowledge, just like me, although you are small children. Similarly, a woman can also understand transcendental knowledge and know what is spirit and what is matter.
Purport: 

These words of Prahlāda Mahārāja are very important in regard to knowledge descending by the disciplic succession. Even when Prahlāda Mahārāja was a baby within the womb of his mother, he became fully convinced of the existence of the supreme power because of hearing the powerful instructions of Nārada and understood how to attain perfection in life by bhakti-yoga. These are the most important understandings in spiritual knowledge.

yasya deve parā bhaktir
 yathā deve tathā gurau
tasyaite kathitā hy arthāḥ
 prakāśante mahātmanaḥ

“Unto those great souls who have implicit faith in both the Lord and the spiritual master, all the imports of Vedic knowledge are automatically revealed.” (Śvetāśvatara Upaniṣad 6.23)

ataḥ śrī-kṛṣṇa-nāmādi
 na bhaved grāhyam indriyaiḥ
sevonmukhe hi jihvādau
 svayam eva sphuraty adaḥ

“No one can understand Kṛṣṇa as He is by the blunt material senses. But He reveals Himself to the devotees, being pleased with them for their transcendental loving service unto Him.” (Bhakti-rasāmṛta-sindhu 1.2.234)

bhaktyā mām abhijānāti
 yāvān yaś cāsmi tattvataḥ
tato māṁ tattvato jñātvā
 viśate tad-anantaram

“One can understand the Supreme Personality as He is only by devotional service. And when one is in full consciousness of the Supreme Lord by such devotion, he can enter into the kingdom of God.” (Bg. 18.55)

These are Vedic instructions. One must have full faith in the words of the spiritual master and similar faith in the Supreme Personality of Godhead. Then the real knowledge of ātmā and Paramātmā and the distinction between matter and spirit will be automatically revealed. This ātma-tattva, or spiritual knowledge, will be revealed within the core of a devotee’s heart because of his having taken shelter of the lotus feet of a mahājana such as Prahlāda Mahārāja.

In this verse the word bhūyāt may be understood to mean “let there be.” Prahlāda Mahārāja offers his blessings to his class friends, saying, “Also become faithful like me. Become bona fide Vaiṣṇavas.” A devotee of the Lord desires for everyone to take to Kṛṣṇa consciousness. Unfortunately, however, people sometimes do not have staunch faith in the words of the spiritual master who comes by the disciplic succession, and therefore they are unable to understand transcendental knowledge. The spiritual master must be in the line of authorized disciplic succession, like Prahlāda Mahārāja, who received the knowledge from Nārada. If the class friends of Prahlāda Mahārāja, the sons of demons, were to accept the truth through Prahlāda, they would certainly also become fully aware of transcendental knowledge.

The words vaiśāradī dhīḥ refer to intelligence concerning the Supreme Personality of Godhead, who is extremely expert. The Lord has created wonderful universes by His expert knowledge. Unless one is extremely expert, he cannot understand the expert management of the supreme expert. One can understand, however, if one is fortunate enough to meet a bona fide spiritual master coming in the disciplic succession from Lord Brahmā, Lord Śiva, Mother Lakṣmī or the Kumāras. These four sampradāyas, or disciplic successions of knowledge and transcendence, are called the Brahma sampradāya, Rudra sampradāya, Śrī sampradāya, and Kumāra sampradāya. Sampradāya-vihīnā ye mantrās te niṣphalā matāḥ. The knowledge of the Supreme received from such a sampradāya, or disciplic succession, can give one enlightenment. If one does not take to the path of disciplic succession, it is not possible for one to understand the Supreme Personality of Godhead. If one understands the Supreme Lord through devotional service with faith in the disciplic succession and then advances further, he awakens his natural love for God, and then his success in life is assured.