Bhagavad Gita Verse 42, Chapter 6

athavaa yoginaameva kule bhavati dheemataam |
etaddhi durlabhataram loke janma yadeedrisham || 42 ||
 
Alternatively, he will go only to a family of learned yogis. One whose birth is of this type is exceedingly rare in this world.
 
athavaa : alternatively
yoginaam : in yogis
eva : only
kule : family
bhavati : will go
dheemataam : learned
etat : this
hi : definitely
durlabhataram : exceedingly rare
loke : world
janma : birth
yat : one whose
eedrisham : of this type
 
Earlier, Shri Krishna spoke about the fate of the unfulfilled meditator who goes to an illustrious family after having attained heaven. In this shloka, Shri Krishna talks about another type of unfilled meditators who is born not into a wealthy family but into a family of learned yogis. He also says that such a birth is exceedingly rare.
 
So far, Shri Krishna has spoken about two types of serious seekers who had a clear understanding of meditation but were unable to attain liberation. The difference between the two types of seekers is the presence or absence of desires. The meditator who still harbours desires is born into a wealthy family.
 
Desires are the biggest obstacles in meditation. Only when desires are extinguished can serious meditation begin. That is why this category of meditators is given the chance to fulfill his desires in a wealthy family.
 
The other rarer category of meditator had managed to extinguish his desires, but could not attain liberation because he ran out of time. Since he is not interested in fulfilling any desire, regardless of whether it is heavenly or earthly, he goes straight into a family of yogis after he dies. These yogis are not just accomplished meditators, they also possess “dheemata” or a keen understanding of the scriptures.
 
Such a family provides a conducive environment for this kind of meditator to continue his progress in meditation. He has enough dispassion in him and therefore does not get affected by the the absence of wealth in this new family. In fact he appreciates it because wealth can become a distraction in the path of meditation.
 
Now, do both these types of newly-born seekers have to start their journey from scratch? This is taken up by Shri Krishna in the next shloka.

Bhagavad Gita Verse 9, Chapter 4

janma karma cha me divyamevam yo vetti tattvataha |
tyaktvaa deham punarjanma naiti maameti sorjuna || 9 ||
 
My birth and action are divine. One who knows this in essence, having given up the body, is not born again; he obtains me, O Arjuna.
 
janma : birth
karma : action
cha : and
me : my
divyam : divine
evam : in this way
yah : one who
vetti : knows
tattvataha : in essence
tyaktvaa : give up
deham : body
punah, janma : rebirth
na : does not
eti : obtain
maam : me
eti : obtain
sah : he
arjuna : O Arjuna
 
In the last two shlokas, Shri Krishna gave the reason for his avataara. Now the question arises: how does this knowledge help the spiritual seeker? He says that once we understand the secret of Ishvaraa's birth and action, we will understand the secret of our action as well.
 
What is the secret of Ishvaraa's birth and action? It looks to us that Ishvaraa is born, and that Ishvaraa performs action. But that is not the case. Through the power of Ishvaraa's Maaya, it only looks like Ishvaraa takes birth and performs action. It is just an illusion. As we have seen earlier, the eternal essence does not perform action, only prakriti - also called maaya - performs action.
 
Now, the jeeva within us is identified with the body, mind and intellect. Its birth is based on past karmaas. It performs karmaas with a sense of doership. In other words, it thinks that it is performing actions. But from the standpoint of the eternal essence, there is no doership or enjoyership. It is prakriti alone that acts. Just like Ishvaraa does not perform action, the jeeva also does not perform action. The jeeva is one with Ishvaraa.
 
So therefore, one who truly and completely understands this point will drop identification with his body, and begin identifying with the eternal essence. That is what is meant by the phrase "deham tvaktvaa": the jeeva has stopped identification of the body.
 
Here, academic knowledge is not enough. We need a first-hand understanding that prakriti performs actions and not the eternal essence. That first-hand understanding can only be gained through meditation, which is explained later in the Gita.
 
A simple way to understand the teaching so far is as follows. The individual jeeva is like a wave in the ocean. Ishvaraa is like the ocean. The eternal essence or brahman is water. Once the wave realizes that it is the same water as Ishvaraa, it is free from the limitations of its tiny form.

Bhagavad Gita Verse 4, Chapter 4

Arjuna uvaacha:
aparam bhavato janma param janma vivasvataha |
kathametadvijaaniyaam tvamaadau proktavaaniti || 4 ||
 
Arjuna said:
Your birth is in the present, and the sun's birth was in the past. How should I understand that you had taught this (yoga) in the beginning?
 
aparam : in the present
bhavatah : you
janma : birth
param : in the past
janma : birth
vivasvataha : the sun
katham : how should
etat : this
vijaaniyaam : understand
tvam : you
aadau : in the beginning
proktavaan : had taught
iti : this
 
Having heard that Shri Krishna taught karmayoga to the sun, Arjuna had a doubt. How could Shri Krishna have revealed this knowledge to the sun? The sun came first before even the earth came into existence. But Shri Krishna was only a little older than Arjuna, so how does one reconcile this fact?
 
Therefore, Arjuna requested Shri Krishna to clarify this point. Even the way he asked this question is very beautiful. He could easily have said "I don't believe you, how is this possible". Instead, he very humbly says "my mind cannot understand this point, please help me understand it". There is no accusation or finger pointing of any sort here. It is asked with sincerity.
 
This question enables Shri Krishna to reveal his true identity to Arjuna in the next shloka.
 
Footnotes
1. Arjuna has referred to Shri Krishna as bhavataha (respected you, or "aap" in hindi) and tvam (friendly you or "tum" in hindi), further highlighting the reverence and friendliness towards Shri Krishna.

Bhagavad Gita Verse 27, Chapter 2

jaatasya hi dhruvoo mrityudhruvam janma mritasya cha |
tasmaadaparihaaryerthe na tvam shoochitumarhasi || 27 ||
 
Since one who is born certainly dies, and one who dies certainly is born. Therefore you should not grieve over this inevitable fact.
 
jaatasya : one who is born
hi : since
dhruvaha : certainly
mrityuha : die
janma : born
mritasya : who is dead
cha : and
tasmaad : therefore
aparihaarye:  inevitable
arthe : fact
na : not
tvam : you
shoochitum : grieve
arhasi : should
 
In the last shloka, Shri Krishna told Arjuna: Even if you think that the eternal essence undergoes birth and death, you should still not grieve. He continues the argument in this shloka.
 
The notion that birth eventually results in death, and death eventually results in birth is sometimes difficult for us to accept emotionally, but at the intellectual level, most of us acknowledge and accept it. I remember watching a TV show that showed a time lapse (high speed) video of a rodent's corpse decaying into the soil, and small plants and flowers emerging from the soil shortly thereafter. I thought that it very vividly and visually illustrated the cyclical nature of birth and death.
 
If we look at this example closely, we conclude that the physical body of the animal transformed into the raw material for the body of the flowers and plants. And although we could not see it, we can guess that the eternal essence of the animal "died" and is now "born" as the life force that sustains the plants and flowers.
 
Therefore we would not grieve for death the animal's body, nor for the death of the life force in it, because both were born again after they died. Similarly, Shri Krishna wanted Arjuna not to grieve for the imminent death of his kinsmen.