The thirteenth chapter of the Bhagavad Gita is Ksetra Ksetrajna Vibhaaga Yoga. The word kshetra means the field, and the kshetrajna means the knower of the field. We can think of our material body as the field and our immortal soul as the knower of the field. In this chapter, Krishna discriminates between the physical body and the immortal soul. He explains that the physical body is temporary and perishable whereas the soul is permanent and eternal. The physical body can be destroyed but the soul can never be destroyed. The chapter then describes God, who is the Supreme Soul. All the individual souls have originated from the Supreme Soul. One who clearly understands the difference between the body, the Soul and the Supreme Soul attains the realization of Brahman.
Through meditation some realize the Self in (their) intellect with the help of the internal organs; others through Sankhya-yoga, and others through Karma-yoga.OPEN VERSE
Others, again, who do not know thus, take to thinking after hearing from others; they, too, who are devoted to hearing, certainly overcome death.OPEN VERSE
O scion of the Bharata dynasty, whatever object, moving or non-moving, comes into being, know that to be from the association of the field and the Knower of the field!OPEN VERSE
He sees who sees the supreme Lord as existing equally in all beings, and as the Imperishable among the perishable.OPEN VERSE
Since by seeing equally God who is present alike everywhere he does not injure the Self by the Self, therefore he attains the supreme Goal.OPEN VERSE
And he who sees actions as being done in various ways by Nature itself, and also the Self as the non-agent, -he sees.OPEN VERSE