Bhagwad Gita- Post 161

Verse 1

Arjuna Uvaacha:

Prakritim purusham chaiva

Kshetram kshetrajnameva cha;

Etadveditumicchaami jnaanam

Jneyam cha keshava.

Arjuna said:

I wish to learn about Nature (matter) and the Spirit (soul), the Field and the Knower of the Field, knowledge and that which ought to be known.

Verse 2

Sri Bhagavaan Uvaacha:

Idam shareeram kaunteya

Kshetramityabhidheeyate;

Etadyo vetti tam praahuh

Kshetrajna iti tadvidah.

The Blessed Lord said:

His body, O Arjuna, is called the Field; he who knows it is called the Knower of the Field by those who know of them, that is, by the sages.

Sri Krishna starts the exposition on the spirit and matter . 

Idaṁ śarīraṁ kaunteya kṣetram ityabhidhīyate 

 “This body, this physical embodiment of the human being, is technically called kṣhetra, or the field where some activity takes place. A field is an area where something happens. 

While this body, which is physical in nature, is a field of operation, there must be somebody who carries on this operation in the field. The field is the body; but the knower of this body is the operator behind it. 

This body is, no doubt, the vehicle of action, but there is somebody who is conscious that there is a body which is to be used for the purpose of some activity. 

This body is an instrument of action in this world, but this body cannot act by itself. It is inert, constituted of the five inert elements—earth, water, fire, air and ether. Inert instruments cannot act by themselves. Even a car cannot move unless there is a driver. So is the case with this body. 

So while this body may be called kṣhetra, or field, the one who knows this field is and is conscious of it, operates through it—lives in it, indwells it, and handles it in a different manner—such a principle is called khṣetrajña.  

Although Krishna uses the words Kshetra and Kshetrajna, various other terms are also used as given below

Kshetra	Kshetrajna
Soarer	Sariri
Deha	Dehi
Jada	Chaitanya

  

Deha and Sarira both mean the body, while Dehi and Sariri both refer to the one who is in the body. 

Since Matter is inert, it is called Jada whereas the knower, the spirit is the Chaitanya. 

Swami says,

“The Sanskrit word Sarira means that which wastes away. It refers to the body. God has been called the Sariri, the one who lives in the perishable body. He has also been called Dehi or the one who lives in the Deha or Body, which is temporary in nature. 

In the Gita, He has been called Kshetrajna, the knower of Kshetra, that which is inert and does not know of itself”

 (Source- Message of the Lord )

Kṣhetrajña iti tadvidaḥ: “Arjuna, I am the knower of the field.” The Lord says, “I am the Pure Consciousness that knows all things and operates these material forces; and I am not merely in one body. 

When I refer to the body, you may be thinking of some particular body, this body or that body, and there is a consciousness in each body. That may be so, that consciousness is inherently present in every body, within each person, but that is not the point.” 

In a sense, it means that the kṣhetra is the entire physical universe. 

The whole of creation can be considered as the kṣhetra, or the field of action; 

and Omniscient Intelligence that is operating in terms of this material manifestation is the kṣhetrajña. 

Therefore, the question of the relationship between God and creation, consciousness and matter, kṣhetrajña  and kṣhetra, purusha and prakriti—all mean, finally, one and the same thing.

Love.