One who is fully surrendered and engaged in the devotional service of the Supreme Lord can understand the Supreme Lord as He is. And as stated in Bhagavad-gītā the Lord gives such a devotee sufficient intelligence so that ultimately the devotee can attain Him in His spiritual kingdom.
(Bhagavad-Gita----8:14----purport).

The Personality of Godhead, being situated in everyone's heart, instructs the devotee regarding pure devotional service so that he may ultimately achieve the association of the Lord. This is confirmed in Bhagavad-gītā (10.10) as follows:
teṣāṁ satata-yuktānāṁ
bhajatāṁ prīti-pūrvakam
dadāmi buddhi-yogaṁ taṁ
yena mām upayānti te
"To one who constantly engages in the devotional service of the Lord with faith and love, the Lord certainly gives the intelligence to achieve Him at the ultimate end."
(Srimad Bhagavatam----3:13:39----purport).

As stated in Bhagavad-gītā (10.10), the Lord gives intelligence to the pure devotees so that they may be elevated to the highest perfectional stage. It is confirmed herein that a pure devotee, who constantly engages in the loving service of the Lord, is awarded all knowledge necessary to reach the Supreme Personality of Godhead. For such a devotee there is nothing valuable to be achieved but the Lord's service. If one serves faithfully, there is no possibility of frustration because the Lord Himself takes charge of the devotee's advancement.
(Srimad Bhagavatam----3:13:49----purport).

The more a devotee engages himself in the devotional service of the Lord, the more encouragement is supplied by the energy of the Lord. In the Bhagavad-gītā the Lord says that to those who are constantly engaged in devotional service with love and affection, the Supreme Personality of Godhead gives intelligence from within, and thus they may make further progress. Being so encouraged, the devotee can never forget, at any moment, the Personality of Godhead. He always feels obliged to Him for having achieved increased power in devotional service by His grace.
(Srimad Bhagavatam----4:9:8----purport).

The Lord is so merciful that not only does He fulfill the desires of a devotee who is driven by ignorance and desires for material benefit, but He also gives such a devotee all protection, just as a cow gives milk to a newly born calf. In the Bhagavad-gītā it is said that the Lord gives intelligence to the constantly engaged devotee so that he may gradually approach the Lord without difficulty. A devotee must be very sincere in his devotional service; then, although there may be many things wrong on the devotee's part, Kṛṣṇa will guide him and gradually elevate him to the highest position of devotional service.
(Srimad Bhagavatam----4:9:17----purport).

As stated in Bhagavad-gītā, dadāmi buddhi-yogaṁ tam. The Lord says, "I give him intelligence." What is that intelligence? Yena mām upayānti te. The Lord gives one the intelligence to cross over the ocean of nescience and come back home, back to Godhead. In conclusion, the cause of all causes, the Absolute Truth, or Supreme Brahman, cannot be understood by philosophical speculation, but He reveals Himself to His devotee because the devotee fully surrenders unto His lotus feet. Bhagavad-gītā is therefore to be accepted as a revealed scripture spoken by the Absolute Truth Himself when He descended to this planet.
(Srimad Bhagavatam----4:11:23----purport).

If a kṛpaṇa, not knowing his self-interest, foolishly asks for something material, one who awards it to him is also foolish. Kṛṣṇa, however, is not a foolish person; He is supremely intelligent. If someone comes to Kṛṣṇa asking for material benefits, Kṛṣṇa does not award him the material things he desires. Instead, the Lord gives him intelligence so that he will forget his material desires and become attached to the Lord's lotus feet. In such cases, although the kṛpaṇa offers prayers to Lord Kṛṣṇa for material things, the Lord takes away whatever material possessions the kṛpaṇa has and gives him the sense to become a devotee.
(Srimad Bhagavatam----6:9:49----purport).

Attachment, greed and lust are three formidable forces that prevent one from concentrating upon the lotus feet of the Supreme Personality of Godhead. These forces act because the Supreme Lord does not like to be realized by nondevotees and atheists. However, when one surrenders unto the lotus feet of the Lord, these impediments are withdrawn, and one can realize the Supreme Personality of Godhead. Therefore the Lord is the protector of the surrendered soul. One cannot become a devotee until one surrenders unto the Lord's lotus feet. Then the Lord gives one the intelligence from within by which one can return home, back to Godhead.
(Srimad Bhagavatam----8:3:28----purport).

Instead of becoming an impersonalist and inviting misfortune and misery, the devotee surrenders to Lord Kṛṣṇa and never suffers in this world. When he leaves his present body, he transcends the material platform and becomes eligible to participate in the Lord's eternal pastimes. As the Supersoul, Lord Kṛṣṇa enlightens the devotee from within the heart and disperses the gloom of ignorance. The Lord gives the devotee the spiritual intelligence to attain Him. The ocean of nescience is very difficult to cross, but when the devotee attempts to cross it, the Lord Himself intervenes to help. Alone the devotee would surely drown, but with the Lord's help he easily crosses over.
(Renunciation Through Wisdom).