Bhagavad Gita Chapter 5.27 - 5.28
sparśān kṛtvā bahir bāhyāḿś
cakṣuś caivāntare bhruvoḥ
prāṇāpānau samau kṛtvā
yaḥ sadā mukta eva saḥ
Shutting out all external sense objects, keeping the eyes and vision concentrated between the two eyebrows, suspending the inward and outward breaths within the nostrils, and thus controlling the mind, senses and intelligence, the transcendentalist aiming at liberation becomes free from desire, fear and anger. One who is always in this state is certainly liberated.