In this verse the particular word brahma is very significant. Brahman refers to one who not only is the greatest, but has the potency to expand to an unlimited extent. How was it possible for Dhruva Mahārāja to capture Brahman within his heart? This question has been very nicely answered by Jīva Gosvāmī. He says that the Supreme Personality of Godhead is the origin of Brahman, for since He comprises everything material and spiritual, there cannot be anything greater than He. In the Bhagavad-gītā also the Supreme Godhead says, "I am the resting place of Brahman." Many persons, especially the Māyāvādī philosophers, consider Brahman the biggest, all-expanding substance, but according to this verse and other Vedic literatures, such as Bhagavad-gītā, the resting place of Brahman is the Supreme Personality of Godhead, just as the resting place of the sunshine is the sun globe. Śrīla Jīva Gosvāmī, therefore, says that since the transcendental form of the Lord is the seed of all greatness, He is the Supreme Brahman. Since the Supreme Brahman was situated in the heart of Dhruva Mahārāja, he became heavier than the heaviest, and therefore everything trembled in all three worlds and in the spiritual world.
The mahat-tattva, or the sum total of the material creation, is to be understood to be the ultimate end of all universes, including all the living entities therein. Brahman is the resort of the mahat-tattva, which includes all material and spiritual entities. It is described in this connection that the Supreme Brahman, the Personality of Godhead, is the master of both pradhāna and puruṣa. Pradhāna means subtle matter, such as ether. puruṣa means the spiritual spark living entities who are entangled in that subtle material existence. These may also be described as parā prakṛti and aparā prakṛti, as stated in Bhagavad-gītā. Kṛṣṇa, being the controller of both the prakṛtis, is thus the master of pradhāna and puruṣa. In the Vedic hymns also the Supreme Brahman is described as antaḥ-praviṣṭaḥ śāstā. This indicates that the Supreme Personality of Godhead is controlling everything and entering into everything. The Brahma-saṁhitā (BS 5.38) further confirms this. Aṇḍāntara-stha-paramāṇu-cayāntara-stham: He has entered not only the universes, but even the atom. In Bhagavad-gītā (BG 10.42) Kṛṣṇa also says, viṣṭabhyāham idaṁ kṛtsnam. The Supreme Personality of Godhead controls everything by entering into everything. By associating constantly with the Supreme Personality in his heart, Dhruva Mahārāja naturally became equal to the greatest, Brahman, by His association, and thus became the heaviest, and the entire universe trembled. In conclusion, a person who always concentrates on the transcendental form of Kṛṣṇa within his heart can very easily strike the whole world with wonder at his activities. This is the perfection of yoga performance, as confirmed in Bhagavad-gītā (BG 6.47). Yoginām api sarveṣām: of all yogīs, the bhakti-yogī, who thinks of Kṛṣṇa always within his heart and engages in His loving transcendental service, is the topmost. Ordinary yogīs can exhibit wonderful material activities, known as aṣṭa-siddhi, eight kinds of yogic perfection, but a pure devotee of the Lord can surpass these perfections by performing activities which can make the whole universe tremble.