Bhagavad Gita 13.2

भगवान श्रीउवाच |
इदं शरीरं कौन्तेय क्षेत्रमित्यभिधीयते |
एतद्यो वेत्ति तं प्राहु: क्षेत्रज्ञ इति तद्विद:

Translation

The Supreme Divine Lord said: O Arjun, this body is termed as kṣhetra (the field of activities), and the one who knows this body is called kṣhetrajña (the knower of the field) by the sages who discern the truth about both.