Blessed by Dhivya Chakshu, Arjuna is having viśvarũpa darshanam of the Lord.  He goes through three stages and his reaction to each stage is different.  First stage is wonder.  Anything in mass scale results in wonder, similar to seeing water in a huge waterfall. 

Verse 23

Oh Lord! People are frightened by seeing your huge form which has many mouths and eyes, which has many arms, thighs, and feet, which has many abdomens, and which is fierce with many tusks also am I frightened.

While witnessing viśvarũpa, Arjuna sees the mouth of the Lord.  The mouth here is the symbol for time principle. Time can be a preserver, protector or destroyer.  Kala as preserver is Brahma, kala as protector is Vishnu and kala as a destroyer is Shiva.  Here Arjuna is looking at the mouth as agni or destructive kala or Shiva and gets frightened.  Viśvarũpa consists of pairs of opposite.  We must accept both aspects of viśvarũpa.  If we see them as a complementary whole, it will not frighten us.  Birth and death are two complementary visions of viśvarũpam.  We should accept both birth and death as mangalam.   We should see everything as undivided part of viśvarũpam, and this is maturity.  If we do not have this maturity, Bhagavan may appear cruel sometimes.  Viśvarũpa as a source of fear is described from verses 23^rd to 30.  Viśvarũpam is fearful for immature people.  Arjuna says the whole world is frightened, and he is also frightened.

Verse 24

Indeed, I am frightened at heart by seeing you who is touching the sky, who is brilliant with many colors, whose mouths are wide open, and who has large fiery eyes.  I do not find courage or composure, Oh, Lord.

Many arms, thighs and feet refer to the arms, thighs, and feet of all the people in the world and not Krishna with many thighs and feet.

Time or kalam has many frightening aspects.  Old age is one of them.  Lord is often named as kala. 

Verse 25

Having just seen Your mouths which are fierce with rusks and which are like the fire of dissolution, I do not recognize the quarters, nor do I find peace.  Be gracious, Oh Lord of lords, who is the abode of the universe.

Arjuna’s mind goes again to the Lord’s mouth.  Protruding teeth symbolize the pain caused by the passing of time. 

At the time of creation, akasha, vayu, agni, jala and prithvi.  At the time of pralaya or end, it happens in reverse order.  Arjuna sees mouth as agni and greatly disturbed. 

Verse 26

All these sons of Dhrudharashtra along with hosts of kings, Bhisma, Drona and that son of charioteer along with the prominent warriors of ours are entering You.

Arjuna does not want to see the mouth, but he is getting a closeup vision of mouth.  Mouth is symbolic of kala and the purpose of mouth eating.  Here the kala refers to the passing of time or getting old and passing away.  We should avoid the fear of old age, decease and death and accept them.

In the battlefield many people are going to die and this verse is the symbolic expression of the death caused by the Mahabharata war.  Arjuna asked for Gita wisdom, because he could not accept the death of Dhrona, Bhishma etc.  But here he is seeing the death of those very same people he had difficulty accepting.  As long as we refuse to accept a situation, life becomes difficult.  Intelligence is accepting choiceless situations.

Verse 27

Speeding, they enter Your terrible moths which are fierce with tusks.  Stuck between the teeth, some of them are seen with their heads crushed.

Arjuna continues to see the frightening mouth of the Lord, with frightening teeth.  This symbolizes different deceases taking away parts of the body. 

Verse 28

These heroes of the world of men enter Your blazing mouths just as many streams of rivers flow towards the ocean only.

All the living-being must be ultimately resolved.  Birth and death are very course of life.  Arjuna gives the example of river.  All rivers rush towards one destination, even though they may take different routes.  That destination is the ocean.  Rivers come from the ocean in the form of rain, and they go back to the ocean.

Verse 29

Again, people enter your mouths with great speed for their own destruction just as moths enter the blazing fire with great speed for their own destruction.

The example given is small insect and fly.  All the insects and flies rush towards flame, even though the flame is going to cause their destruction.  But they are attracted by the brightness of the flame and fly into their own death.  Similarly, we are all rushing towards the death by the passing of time.  Kala tattvam is described as part of viśvarũpa darshanam.   Atma is the only place where kala and desha (time and form) is absent and atma tattvam is the only solution.  As long as we are away from atma, we should accept kala and desha, old age and ultimate death.