Bhagavad Gita Verse 27, Chapter 5

sparshaankritvaa bahirbaahyaanshchakshushchaivaantare bhruvooho |
praanaapaanau samau kritvaa naasaabhyantarachaarinau || 27 ||
 
Keeping external sense objects outside, and eyes in the center of the eyebrows, and also equalizing the incoming and outgoing flow of breath inside the nostrils;
 
sparshaan : sense objects
kritvaa : keeping
bahihi : outside
baahyaan : external
chakshuhu : eyes
cha : and
eva : also
antare : center
bhruvooha : the eyebrows
praanaapaanau : incoming and outgoing breath
samau : equal
kritvaa : making
naasa : nostrils
abhyantara : inside
chaarinau : flow of breath through nostrils
 
Shri Krishna gives a preview of the upcoming chapter on dhyaana yoga or meditation in this and the next shloka. He explains the technique of meditation in a nutshell, but goes into the details in the next chapter. In a nutshell, the technique involves clearing the mind of all external sense object impressions, keeping eyes focused on one point, and equalizing the incoming and outgoing breath.
 
The eternal essence cannot be realized if the mind is dwelling on sense objects, therefore the technique requires us to temporarily cut off connection with sense objects. Practically, we cannot shut off the world completely i.e. if we hear a sound somewhere, it will enter into our ears. The point is that we should not let our mind chase any sense perception. Further, even if the mind is not receiving sensory inputs, it should be restrained from going into the past or the future.
 
Next, Shri Krishna asks us to focus the eyes in the middle of the eyebrows. This is because the eyes follow the mind and its thoughts. If the mind is restless, the eyes will wander. So keeping the eyes steady has the effect of stabilizing the mind. In the same way, if the mind is restless, it is reflected in the breath. So we are asked to balance the incoming and outgoing breath with the aim of calming the mind. If the breathing becomes harmonious, we know that the mind has become calm.
 
So in this manner, Shri Krishna describes how we should physically prepare ourself for meditation. In the next shloka, he points out the internal preparation. We notice that this shloka ends in mid-sentence. The rest of the sentence is found in the next shloka.