The Brahma-saṁhitā (5.33) says:

advaitam acyutam anādim ananta-rūpam ādyaṁ purāṇa-puruṣaṁ nava-yauvanaṁ ca vedeṣu durlabham adurlabham ātma-bhaktau govindam ādi-puruṣaṁ tam ahaṁ bhajāmi

“I worship the Supreme Personality of Godhead, Govinda [Kṛṣṇa], who is the original person — absolute, infallible, without beginning, although expanded into unlimited forms, still the same original, the oldest, and the person always appearing as a fresh youth. Such eternal, blissful, all-knowing forms of the Lord cannot be understood even by the best Vedic scholars, but they are always manifest to pure, unalloyed devotees.” The Supreme Personality of Godhead has no cause, for He is the cause of everything. The Lord is beyond the workings of cause and effect. He is eternally existing. In another verse the Brahma-saṁhitā says, aṇḍāntara-stha-paramāṇu-cayāntara-stham: the Lord exists within the gigantic universe and within the atom. The descent of the Lord into the atom and the universe indicates that without His presence, nothing could factually exist. Scientists say that water is a combination of hydrogen and oxygen, but when they see a vast ocean they are puzzled about where such a quantity of hydrogen and oxygen could have come from. They think that everything evolved from chemicals, but where did the chemicals come from? That they do not know. Since the Supreme Personality of Godhead is the cause of all causes, He can produce immense quantities of chemicals to create a situation for chemical evolution. We actually see that chemicals are produced from living entities. For example, a lemon tree produces many tons of citric acid. The citric acid is not the cause of the tree; rather, the tree is the cause of the acid. Similarly, the Supreme Personality of Godhead is the cause of everything. He is the cause of the tree that produces the citric acid ( bījaṁ māṁ sarva-bhūtānām ). Devotees can see that the original potencies causing the cosmic manifestation are not in chemicals but in the Supreme Personality of Godhead, for He is the cause of the chemicals.

Everything is caused or manifested by the energy of the Supreme Lord, and when everything is annihilated or dissolved, the original potency enters the body of the Supreme Lord. Therefore this verse says, ādāv ante ’pi ca sattvānāṁ yad dhruvaṁ tad evāntarāle ’pi. The word dhruvam means “permanent.” The permanent reality is Kṛṣṇa, not this cosmic manifestation. As stated in Bhagavad-gītā, aham ādir hi devānām and mattaḥ sarvaṁ pravartate: Kṛṣṇa is the original cause of everything. Arjuna recognized Lord Śrī Kṛṣṇa as the original person ( puruṣaṁ śāśvataṁ divyam ādi-devam ajaṁ vibhum ), and the Brahma-saṁhitā describes Him as the original person ( govindam ādi-puruṣam ). He is the cause of all causes, whether at the beginning, at the end or in the middle.