Srimad Bhagavatam Canto 11, Chapter 24, Text 11

SB 11.24.11

so ’srjat tapasa yukto
 rajasa mad-anugrahat
lokan sa-palan visvatma
 bhur bhuvah svar iti tridha
 
Translation: 
 
Lord Brahma, the soul of the universe, being endowed with the mode of passion, performed great austerities by My mercy and thus created the three planetary divisions, called Bhur, Bhuvar and Svar, along with their presiding deities.
Srimad Bhagavatam Canto 11, Chapter 24, Text 10
Srimad Bhagavatam Canto 11, Chapter 24, Text 12