The Lord rested on the causal ocean and expanded his yoga nidra, when out of his navel lake a lotus arose, and out of that lotus, the lord of the prajapatis, Brahma, arose.
English translation and commentary of Srimad Bhagavatam. Adapted from the Hindi commentary of Srimad Bhagavatam by Maharajshri Shri Akhandanand Saraswati Maharaj