BG Chap 10 - Kṛṣṇa illuminates the hearts of His devotees
To show special mercy to devotees, who cannot live without the Lord, Kṛṣṇa destroys the darkness born of ignorance with the shining lamp of knowledge. This knowledge arises from bhakti, which is beyond the guṇas, and not sāttvika knowledge. Like a bee inside the whorl of the lotus, Kṛṣṇa is situated with attachment for the devotees, and He reveals His dazzling form and qualities. He destroys darkness in the form of desires for objects other than Himself born from ignorance in the form of anādi-karma which covers knowledge. Kṛṣṇa bears the responsibility for elevating their intelligence and destroy the ignorance within. He accepts responsibility to supply all their material and spiritual requirements, without their striving for it.
The Lord tells Arjuna that basically there is no possibility of understanding the Supreme Truth, the Absolute Truth, the Supreme Personality of Godhead, simply by speculating, for the Supreme Truth is so great that it is not possible to understand Him or to achieve Him simply by making a mental effort. Man can go on speculating for several millions of years, and if he is not devoted, if he is not a lover of the Supreme Truth, he will never understand Kṛṣṇa, or the Supreme Truth. Only by devotional service is the Supreme Truth, Kṛṣṇa, pleased, and by His inconceivable energy He can reveal Himself to the heart of the pure devotee. The pure devotee always has Kṛṣṇa within his heart; and with the presence of Kṛṣṇa, who is just like the sun, the darkness of ignorance is at once dissipated. This is the special mercy rendered to the pure devotee by Kṛṣṇa.
The four verses of Gītā (10.8 – 10.11) are the essence of Bhagavad-gītā and they are thus called the catuḥ-ślokī Gītā. The intelligent people understand that what is proclaimed in the ninth and tenth chapters, the very womb of the Gītā, is the essential meaning of the Gītā. They remove the distress of all living beings and bring about all auspiciousness.