Here is the Sanskrit anuvad, Hindi anuvad, and English translation of Ksetra-Ksetrajna-Vibhaga Yoga Chapter 13, Verse 13.1.
Sanskrit
अर्जुन उवाच । प्रकृतिं पुरुषं चैव क्षेत्रं क्षेत्रज्ञमेव च एतद्वेदितुमिच्छामि ज्ञानं ज्ञेयं च केशव…
Hindi
श्रीभगवान् बोले- हे अर्जुन ! यह शरीर ‘क्षेत्र १ इस नामसे कहा जाता है और इसको जो जानता है, उसको ‘क्षेत्रज्ञ’ इस नामसे उनके तत्त्वको जाननेवाले ज्ञानीजन कहते हैं|
English
The Blessed Lord said: This body, O Arjuna, is called Kshetra (the field); he who knows it is called Kshetragya (the knower of the field) by the sages (those who have acquired spiritual knowledge).