Lord Krishna says:
They [the Vedas] speak of an indestructible Āśvattha tree with its roots above and branches below, the leaves of which are the Vedic hymns. The one who knows this tree knows the Vedas.

Its branches are spread out both above and below, nourished by the guṇas. The objects of the senses are the shoots. The roots extend downward into this material world where they combine with action that gives results.

Its form cannot be fully perceived for it has no end, beginning or foundation. But using the strong weapon of detachment, one should cut down this firmly-rooted Āśvattha tree.

One should then seek that realm, which once attained, one never comes back from; there he should surrender to the Supreme Lord from where this whole process emanated.

Free from pride and foolishness, having conquered the obstacle of attachment, in constant pursuit of the spiritual goal, having rejected material desire and been liberated from the pairs of opposites known as pleasure and pain, the undeluded one attains that Supreme Abode.

That supreme realm of Mine, is not illumined by the Sun or the Moon, nor by fire. After reaching this place one does not return again.

An eternal fragment of Myself becomes embodied as the living beings – jīvas – within this mortal world. It acquires the five senses, and the mind, which is the sixth, all of which reside in this material nature.

Whatever body the Self acquires or departs from, It proceeds, taking with It these six sense-faculties, just as the wind carries a fragrance from place to place.

Presiding over the ear, the eye, the sense of touch, the tongue, the nose, and the mind, the Self experiences the objects of the senses.

Joined with the guṇas, when departing, staying or experiencing, the deluded persons cannot perceive the Self. But those who possess the eye of knowledge can.

The practitioners of yoga are able to see the Self abiding within themselves, but those who lack intelligence and have not mastered themselves cannot behold It even if they strive for It.

You should know that the energy of the Sun, which illumines the whole universe, and the energy of the Moon and fire, are Mine alone.

Pervading the Earth, I support all beings with My power. I nourish all herbs by becoming the Moon, full of potency.

Becoming the digestive fire, I function within the bodies of all living beings. By joining with the prāṇa and the apāṇa air breaths, I digest the four kinds of food.

And I dwell in the hearts of all. From Me comes knowledge, memory and loss of memory. Indeed, I alone am that which is to be known from all the Vedas. I am the creator of Vedānta and I alone am the knower of the Vedas.

Beings exists in two distinct forms: perishable and imperishable. The material body bound to the material world is perishable, while the immutable Self is imperishable.

But different and beyond these two forms, is the highest Puruṣa, described as the Supreme Self or Supersoul (Paramātma), He is the unchanging Lord who pervades the three worlds and supports it.

Because I transcend the perishable and am also higher than the imperishable, I am declared in the world and by the Vedas as the Supreme Being (Puruṣottama).

Whoever is not deluded and understands Me as the highest Puruṣa, knows all. He worships Me with his whole being.

O sinless one, I have now revealed the most mysterious doctrine. By understanding this, O Arjuna, one will become truly wise and would have fulfilled all duties.