Closing all the doors formed by the senses the Understanding should be with-drawn into the mind. In this condition when absorbed in contemplation, it acquires the knowledge of Brahma.
सर्वाण्येतानि संवार्य द्वाराणि मनसि स्थितः। मनस्येकाग्रतां कृत्वा तत्परं प्रतिपद्यते॥