Bhagavad Gita · 13.3

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

kṣhetrajñaṁ chāpi māṁ viddhi sarva-kṣhetreṣhu bhārata kṣhetra-kṣhetrajñayor jñānaṁ yat taj jñānaṁ mataṁ mama

Know me also as the Knower of the Field in all fields, O Bharata. The knowledge of the field and the knower of the field — that I consider to be true knowledge.

— Bhagavad Gita 13.3

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)