क्षेत्रज्ञं चापि मां विद्धि सर्वक्षेत्रेषु भारत ।
क्षेत्रक्षेत्रज्ञयोर्ज्ञानं यत्तज्ज्ञानं मतं मम ।। १३.२ ।।

kṣetra-jñaṁ cāpi māṁ viddhi sarva-kṣetreṣu bhārata |
kṣetra-kṣetrajñayor-jñānaṁ yat-taj-jñānaṁ mataṁ mama || 13.2 ||

Next he adds:

Arjuna, in all the kshetras (fields), know the supreme Reality (Me) as kshetrajna (knower of the kshetra). The knowledge of both kshetra and kshetrajna is, according to me, true spiritual wisdom.

Bodies are many, each being different from the other. Also, there is ample variety in the bodily level. But in the Knower of the body, the kshetrajna, no such difference reigns. Krishna declares that in all the kshetras, the kshetrajna is but one. The lesson of spirituality begins with as well as subsists on this oneness.