SB 1.2 - Who should we worship?
One may ask should not we serve the powerful deities Brahmā, Viṣṇu and Śiva. Sūta describes the relationship between these deities and Kṛṣṇa.
The Lord is indirectly associated with the three modes of nature. For the material world’s creation, maintenance and destruction He accepts the three qualitative forms of Brahmā, Viṣṇu and Śiva. Of these three, all human beings can derive ultimate benefit from Viṣṇu, the form of the quality of goodness, which increases knowledge. It has just been explained that one should perform bhakti alone rather than karma or jñāna. Similarly one should worship Bhagavān alone, giving up the worship of the demigods.
Lord Kṛṣṇa and all His plenary parts are viṣṇu-tattva. From Kṛṣṇa, the next manifestation is Baladeva. From Baladeva is Saṅkarṣaṇa, from Saṅkarṣaṇa is Nārāyaṇa, from Nārāyaṇa there is the second Saṅkarṣaṇa, and from this Saṅkarṣaṇa the puruṣa-avatāras. The Viṣṇu or the Deity of the quality of goodness in the material world is the puruṣa-avatāra known as Kṣīrodakaśāyī Viṣṇu or Paramātmā. Brahmā is the deity of passion, and Śiva of ignorance. The materialists and the foolish worship Brahmā and Śiva respectively. But the pure transcendentalists worship the form of goodness, Viṣṇu, in His various forms. The integrated forms of the Lord are called Godhead, and the separated forms are called the jīvas. Both the jīvas and Godhead have their original spiritual forms.
The avatāras are of two types: those related to cit-śakti and those related to māyā-śakti. Those related to cit-śakti such as Matsya and Kūrma are to be worshiped. Those related to māyā-śakti thru sattva, rajas and tamas, are Viṣṇu, Brahmā and Śiva. Among them Viṣṇu is to be worshiped. When Viṣṇu appears in the material world He comes to deliver the living beings who are under the material energy. Such living beings come to the material world to become lords, and thus become entrapped by the three modes of nature. The prison house of the material world is created by Brahmā under instruction of the Personality of Godhead, and at the conclusion of a kalpa the whole thing is destroyed by Śiva. The maintenance is done by Lord Viṣṇu. Anyone, therefore, wishing to get out of material existence must please Viṣṇu for such liberation. Anyone wishing to continue his prison life in material existence may ask for relative facilities for temporary relief from the different demigods like Śiva, Brahmā and others. But only Viṣṇu can release a living being from the conditioned life of material existence and no one else.