SB 11.4.5
adav abhuc chata-dhrti rajasasya sarge
visnuh sthitau kratu-patir dvija-dharma-setuh
rudro ’pyayaya tamasa purusah sa adya
ity udbhava-sthiti-layah satatam prajasu
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In the beginning, the original Supreme Personality manifested the form of Brahma through the material mode of passion in order to create this universe. The Lord manifested His form as Visnu, the Lord of sacrifice and protector of the twice-born brahmanas and their religious duties, to maintain the universe. And when the universe is to be annihilated the same Supreme Lord employs the material mode of ignorance and manifests the form of Rudra. The created living beings are thus always subject to the forces of creation, maintenance and destruction.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In the previous verse the Supreme Personality of Godhead was described as adi-karta, the original person responsible for the creation, maintenance and annihilation of the material world. According to Sridhara Svami, adi-karta, or “the original doer,” implies subsequent creators, maintainers and annihilators. Otherwise there would be no meaning to the word adi, or “original.” Therefore this verse describes that the Absolute Truth expands Himself into the gunavataras, or incarnations who carry out the creation, maintenance and annihilation of the universe through the modes of passion, goodness and ignorance respectively.
It is significant here that although this verse mentions creation through the material mode of passion and annihilation through the material mode of ignorance, it does not mention maintenance by Visnu through the material mode of goodness. That is because Visnu is visuddha-sattva, or existing on the platform of unlimited transcendental goodness. Although Lord Siva and Lord Brahma are somewhat affected by their prescribed duties as superintendents of the modes of nature, Lord Visnu is visuddha-sattva, completely beyond contamination even by the material mode of goodness. As described in the Vedas, na tasya karyam karanam ca vidyate: the Lord has no occupational duty. Whereas Lord Siva and Lord Brahma are understood to be servants of the Lord, Visnu is completely transcendental.
According to Srila Jiva Gosvami, Visnu, described in this verse as kratu-patih, the Lord of sacrifice, is understood to have appeared in a previous age as the incarnation Suyajña, the son of Prajapati Ruci. Whereas Brahma and Siva faithfully engage in service to the Supreme Lord, Visnu is the Supreme Lord Himself, and therefore His activities of maintaining the brahmanas and religious principles, as mentioned in this verse (dvija-dharma-setuh), are not occupational duties but lila. So in addition to being a gunavatara, Visnu is also a lilavatara, according to Srila Jiva Gosvami. The Mahabharata (Santi-parva) describes the birth of Lord Brahma from the lotus flower emanating from Visnu and the subsequent birth of Lord Siva from the angry eyes of Lord Brahma. Visnu, however, is the self-manifested Personality of Godhead who enters the material universe by His own internal potency, as stated in Srimad-Bhagavatam (3.8.15):
tal loka-padmam sa u eva visnuh
pravivisat sarva-gunavabhasam
In conclusion, Lord Visnu, the Supreme Personality of Godhead, is the supreme controller whose personal form is full of eternal existence, knowledge and bliss, who is beginningless but is the beginning of everything, who is known as Govinda, and who is the original cause of all causes, as stated in Brahma-samhita. Still, that same eternal Lord manifests Himself as Brahma and Siva in the sense that the primeval controllers Brahma and Siva manifest the potency and supreme will of the Lord, although they themselves are not supreme.