SB 11.24.13
adho ’suranam naganam
bhumer oko ’srjat prabhuh
tri-lokyam gatayah sarvah
karmanam tri-gunatmanam
Translation:
Lord Brahma created the region below the earth for the demons and the Naga snakes. In this way the destinations of the three worlds were arranged as the corresponding reactions for different kinds of work performed within the three modes of nature.