Bhagwad Gita Chapter 15

Krishna said: There is a banyan tree which has its roots upward and its branches down and whose leaves are the Vedic hymns. One who knows this tree is the knower of the Vedas. The branches of this tree extend downward and upward, nourished by the three modes of material nature. The twigs are the objects of the senses. This tree also has roots going down, and these are bound to the fruitive actions of human society. The real form of this tree cannot be perceived in this world. No one can understand where it ends, where it begins, or where its foundation is.

One who is free from illusion, false prestige, and false association, who understands the eternal, who is done with material lust and is freed from the duality of happiness and distress, and who knows how to surrender unto the Supreme Person, attains to that eternal kingdom.

The living entities in this conditioned world are My eternal, fragmental parts. Due to conditioned life, they are struggling very hard with the six senses, which include the mind.The living entity in the material world carries his different conceptions of life from one body to another as the air carries aromas.

One who is a self realized soul can see all this clearly. But those who are not cannot see what is taking place, though they may try to. The splendor of the sun comes from Me. The splendor of the moon and the splendor of fire are also from Me. I enter into each planet, and by My energy they stay in orbit. I become the moon and thereby supply the juice of life to all vegetables. I am the fire of digestion in every living body, and I am the air of life, outgoing and incoming, by which I digest the four kinds of foodstuff. I am seated in everyone's heart, and from Me come remembrance, knowledge and forgetfulness. By all the Vedas am I to be known; indeed I am the compiler of Vedanta, and I am the knower of the Vedas. There are two classes of beings, the fallible and the infallible. In the material world every entity is fallible, and in the spiritual world every entity is called infallible.
Besides these two, there is the greatest living personality, the Lord Himself, who has entered into these worlds and is maintaining them. Because I am transcendental, beyond both the fallible and the infallible, and because I am the greatest, I am celebrated both in the world and in the Vedas as that Supreme Person.Whoever knows Me as the Supreme Personality of Godhead, without doubting, is to be understood as the knower of everything, and he therefore engages himself in full devotional service, Arjuna. This is the most confidential part of the Vedic scriptures, O sinless one, and it is disclosed now by Me. Whoever understands this will become wise, and his endeavors will know perfection.