Chapter 8, Verse 12
Part of 8: Akṣhar Brahma Yog — अक्षरब्रह्मयोगसर्वद्वाराणि संयम्य मनो हृदि निरुध्य च। मूर्ध्न्याधायात्मनः प्राणमास्थितो योगधारणाम्॥
sarva-dvārāṇi sanyamya mano hṛidi nirudhya cha mūrdhnyādhāyātmanaḥ prāṇam āsthito yoga-dhāraṇām
Having closed all the gates, confined the mind in the heart, and fixed the life-breath in the head, engage in the practice of concentration.
The gates are the senses of knowledge. Closing the gates means control of all senses by the practice of Pratyahara or withdrawal of the consciousness from them. Even if the senses are controlled, the mind will be dwelling on the sensual objects. Therefore the mind is confined or fixed in the lotus of the heart and thery all the thoughts or mental modifications are also controlled. The whole lifreath is now taken up and fixed at the crown of the head (Brahmarandhra or the hole of Brahman).