When the intelligence of the gigantic form separately became manifest, Brahmā, the lord of the Vedas, entered into it with the partial power of understanding, and thus an object of understanding is experienced by the living entities.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
बुद्धिं चास्य विनिर्भिन्नां वागीशो धिष्ण्यमाविशत् । बोधेनांशेन बोद्धव्यप्रतिपत्तिर्यतो भवेत्
buddhiṃ cāsya vinirbhinnāṃ vāgīśo dhiṣṇyamāviśat | bodhenāṃśena boddhavyapratipattiryato bhavet
SB 3.6.23