Srimad Bhagavatam Canto 04, Chapter 01, Text 30

SB 4.1.30

deva ucuh
yatha krtas te sankalpo
bhavyam tenaiva nanyatha
sat-sankalpasya te brahman
yad vai dhyayati te vayam
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
The three deities told Atri Muni: Dear brahmana, you are perfect in your determination, and therefore as you have decided, so it will happen; it will not happen otherwise. We are all the same person upon whom you were meditating, and therefore we have all come to you.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
 
Atri Muni unspecifically thought of the Personality of Godhead, the Lord of the universe, although he had no clear idea of the Lord of the universe nor of His specific form. Maha-Visnu, from whose breathing millions of universes emanate and into whom they are again withdrawn, may be accepted as the Lord of the universe. Garbhodakasayi Visnu, from whose abdomen sprouted the lotus flower which is the birthplace of Brahma, may also be considered the Lord of the universe. Similarly, Ksirodakasayi Visnu, who is the Supersoul of all living entities, may also be considered the Lord of the universe. Then, under the order of Ksirodakasayi Visnu, the Visnu form within this universe, Lord Brahma and Lord Siva may also be accepted as the Lords of the universe.
 
Visnu is the Lord of the universe because He is its maintainer. Similarly, Brahma creates the different planetary systems and the population, so he also may be considered the Lord of the universe. Or Lord Siva, who is ultimately the destroyer of the universe, also may be considered its Lord. Therefore, since Atri Muni did not specifically mention whom he wanted, all three Brahma, Visnu and Lord Siva came before him. They said, “Since you were thinking of having a son exactly like the Supreme Personality of Godhead, the Lord of the universe, your determination will be fulfilled.” In other words, one’s determination is fulfilled according to the strength of one’s devotion. As stated in Bhagavad-gita (9.25): yanti deva-vrata devan pitrn yanti pitr-vratah. If one is attached to a particular demigod, one is promoted to the abode of that demigod; if one is attached to the Pitas, or forefathers, one is promoted to their planet; and similarly if one is attached to the Supreme Personality of Godhead, Krsna, one is promoted to the abode of Lord Krsna. Atri Muni had no clear conception of the Lord of the universe; therefore the three presiding deities who are actually the lords of the universe in the three departments of the modes of nature all came before him. Now, according to the strength of his determination for a son, his desire would be fulfilled by the grace of the Lord.
Srimad Bhagavatam Canto 04, Chapter 01, Text 29
Srimad Bhagavatam Canto 04, Chapter 01, Text 31