You can also check this, Chapter VIII: "The Way To Eternal Brahman"
ARJUNA: Tell me, Krishna, what Brahman is. What is the Atman, and what is the creative energy of Brahman? Explain the nature of this relative world, and of the individual man.
Who is God who presides over action in this body, and how does He dwell here? How are you revealed at the hour of death to those whose consciousness is united with you?
SRI KRISHNA: Brahman is that which is immutable, and independent of any cause but Itself. When we consider Brahman as lodged within the individual being, we call Him the Atman. The creative energy of Brahman is that which causes all existences to come into being.
The nature of the relative world is mutability. The nature of the individual man is his consciousness of ego. I alone am God who presides over action, here in this body.
At the hour of death, when a man leaves his body, he must depart with his consciousness absorbed in me. Then he will be united with me. Be certain of that. Whatever a man remembers at the last, when he is leaving the body, will be realized by him in the hereafter; because that will be what his mind has most constantly dwelt on, during this life.
Therefore you must remember me at all times, and do your duty. If your mind and heart are set upon me constantly, you will come to me. Never doubt this.
Make a habit of practicing meditation, and do not let your mind be distracted. In this way you will come finally to the Lord, who is the light-giver, the highest of the high.
He is all-knowing God, lord of the emperors,
Ageless, subtler far than mind's inmost subtlety,
Universal sustainer,
Shining sunlike, self luminous.
What fashion His form has, who shall conceive of it?
He dwells beyond delusion, the dark of Maya.
On Him let man meditate
Always, for then at the last hour
Of going hence from his body he will be strong
In the strength of this yoga, faithfully followed:
The mind is firm, and the heart
So full, it hardly holds its love.
Thus he will take his leave: and now, with the life-force
Indrawn utterly, held fast between the eyebrows,
He goes forth to find his Lord,
That light-giver, who is greatest.
Now I will tell you briefly about the nature of Him who is called the deathless by those seers who truly understand the Vedas. Devotees enter into Him when the bonds of their desire are broken. To reach this goal, they practice control of the passions.
When a man leaves his body and departs, he must close all the doors of the senses. Let him hold the mind firmly within the shrine of the heart, and fix the life-force between the eyebrows. Then let him take refuge in steady concentration, uttering the sacred syllable OM and meditating upon me. Such a man reaches the highest goal. When a yogi has meditated upon me unceasingly for many years, with an undistracted mind, I am easy of access to him, because he is always absorbed in me.
Great souls who find me have found the highest perfection. They are no longer reborn into this condition of transience and pain.
All the worlds, and even the heavenly realm of Brahma, are subject to the laws of rebirth. But for the man who comes to me, there is no returning.
There is day, also, and night in the universe:
The wise know this, declaring the day of Brahma
A thousand ages in span
And the night a thousand ages.
Day dawns, and all those lives that lay hidden asleep
Come forth and show themselves, mortally manifest:
Night falls, and all are dissolved
Into the sleeping germ of life.
Thus they are seen, O Prince, and appear unceasingly,
Dissolving with the dark, and with day returning
Back to the new birth, new death:
All helpless. They do what they must.
But behind the manifest and the unmanifest, there is another Existence, which is eternal and changeless. This is not dissolved in the general cosmic dissolution. It has been called the unmanifest, the imperishable. To reach it is said to be the greatest of all achievements. It is my highest state of being. Those who reach It are not reborn. That highest state of being can only be achieved through devotion to Him in whom all creatures exist, and by whom this universe is pervaded.
I show you two paths.
Let a yogi choose either
When he leaves this body:
The Path that leads back to birth,
The path of no return.
There is the path of light,
Of fire and day,
The path of the moon's bright fortnight
And the six months' journey
Of the sun to the north:
The knower of Brahman
Who takes this path
Goes to Brahman:
He does not return.
There is the path of night and smoke,
The path of the moon's dark fortnight
And the six months' journey
Of the sun to the south:
The yogi who takes this path
Will reach the lunar light:
This path leads back
To human birth, at last.
These two paths, the bright and the dark, may be said to have existed in this world of change from a time without any beginning. By the one, a man goes to the place of no return. By the other, he comes back to human birth. No yogi who knows these two paths is ever misled. Therefore, Arjuna, you must be steadfast in yoga, always.
The scriptures declare that merit can be acquired by studying the Vedas, performing ritualistic sacrifices, practicing austerities and giving alms. But the yogi who has understood this teaching of mine will gain more than any who do these things. He will reach that universal source, which is the uttermost abode of God.
