samavetān yathā purā

kada-cit-once upon a time; dhyayatah-while contemplating; srastuh-of Brahma; vedah-the Vedic literature; asan-became manifested; catur-mukhat-from the four mouths; katham sraksyami-how shall I create; aham-myself; lokan-all these worlds; samavetan-assembled; yatha-as they were; pura-in the past.