Brahmā, born out of the lotus flower, could not see the world, although he was situated in the whorl. He therefore circumambulated all of space, and while moving his eyes in all directions he achieved four heads in terms of the four directions.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
तस्यां स चाम्भोरुहकर्णिकाया- मवस्थितो लोकमपश्यमानः । परिक्रमन् व्योम्नि विवृत्तनेत्र- श्चत्वारि लेभेऽनुदिशं मुखानि
tasyāṃ sa cāmbhoruhakarṇikāyā- mavasthito lokamapaśyamānaḥ | parikraman vyomni vivṛttanetra- ścatvāri lebhe'nudiśaṃ mukhāni
SB 3.8.16