Text 27-28

sparshan kritva bahir bahyams
caksus caivantare bhruvoh
pranapanau samau kritva
nasabhyantara-carinau

yatendriya-mano-buddhir
munir moksha-parayanah
vigateccha-bhaya-krodho
yah sada mukta eva sah

Translation

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. 

Commentary by Srila Prabhupada 

Being engaged in Krishna consciousness, one can immediately understand one’s spiritual identity, and then one can understand the Supreme Lord by means of devotional service. When one is well situated in devotional service, one comes to the transcendental position, qualified to feel the presence of the Lord in the sphere of one’s activity. This particular position is called liberation in the Supreme. 

After explaining the above principles of liberation in the Supreme, the Lord gives instruction to Arjuna as to how one can come to that position by the practice of the mysticism or yoga known as ashtanga-yoga, which is divisible into an eightfold procedure called yama, niyama, asana, pranayama, pratyahara, dharana, dhyana and samadhi. In the Sixth Chapter the subject of yoga is explicitly detailed, and at the end of the Fifth it is only preliminarily explained. One has to drive out the sense objects such as sound, touch, form, taste and smell by the pratyahara process in yoga, and then keep the vision of the eyes between the two eyebrows and concentrate on the tip of the nose with half-closed lids. There is no benefit in closing the eyes altogether, because then there is every chance of falling asleep. Nor is there benefit in opening the eyes completely, because then there is the hazard of being attracted by sense objects. The breathing movement is restrained within the nostrils by neutralizing the up-moving and down-moving air within the body. By practice of such yoga one is able to gain control over the senses, refrain from outward sense objects, and thus prepare oneself for liberation in the Supreme. 

This yoga process helps one become free from all kinds of fear and anger and thus feel the presence of the Supersoul in the transcendental situation. In other words, Krishna consciousness is the easiest process of executing yoga principles. This will be thoroughly explained in the next chapter. A Krishna conscious person, however, being always engaged in devotional service, does not risk losing his senses to some other engagement. This is a better way of controlling the senses than by the ashtanga-yoga.

Commentary by Sri Visvanatha Cakravarti Thakur

The heart becomes purified by performance of niskama karma yoga offered to the Lord. Then arises jnana, whose subject is the soul (tvam). Then arises bhakti, for gaining knowledge of the Lord (tat). By the appearance of that knowledge of the Lord which is beyond the modes, one gains realization of brahman. This has been stated in this chapter.

Now in three verses 27-29, the Lord speaks in abbreviated form what he will explain in the sixth chapter: that the process of astanga yoga,  practiced  after  having purified  the  heart by niskama karma yoga, is shown to be superior to the process of jfiana yoga for producing realization of brahman.

The word sparsan (touches) stands for all the sense objects-sound, touch, form, taste and smell. Externalizing these from the mind when they enter, that is, withdrawing the mind from the sense objects (pratyahara), placing the eyes between the eye brows, with half closed eyes, the yogi should fix his glance between the brows in order to prevent both sleep and wandering eyes. By extinguishing the upward and downward motions of the prana and apana which move in the nostrils though inhaling and exhaling, one makes them equal. By that means, the senses mind and intelligence are brought under control.