The fifteenth chapter, called "Purushottama Yoga" or "The Supreme Purusha in the light of Yoga", tells us of Asvattha the great tree of life and of how God takes birth in Prakriti. We are also told of the three Purushas Jivatman (also called Bhutatman, mortal), the Individual soul (immortal) and the Supreme Purusha (Krishna Himself or God).
The Blessed Lord said:
They say the eternal Asvattha
Above, below, its branches do extend,
Its real form can never be perceived,
A person seeketh for that happy goal,
From pride, delusion, and attachment free,
The Sun does not illumine it;
An eternal portion of myself
And when the Lord a body takes,
Presiding over the ear and eye,
Quitting a form, or dwelling there,
The Yogis, striving, see the Lord,
The light that dwelleth in the Sun,
Entering the earth, do I support
And I become the fire of life,
And I abide within the hearts of all;
There are two Purushas in the world,
There is yet a greater Purusha still,
As I transcend the mortal one
And he who from delusion free,
And thus have I, O sinless one,
Asvattha: It is the scared Fig Tree, the Tree of Life.
Weapons of detachment: We can escape the taint of life's activities only by means of detachment.
When God takes birth in this world of life, he makes use of the different forms of Prakriti.
Two Purushas: These are two aspects of the individual soul, the soul in itself, and when it is associated with the objects of life, and becomes Bhutatman, Jivatman, or Egoism (Ahankara). In the Upanishads this difference is indicated by the simile of two birds who dwell in the same tree, one whom partakes of the fruit, and the other does not.
A greater Purusha still: This is God, the Supreme Purusha.