Bhagavad Gita · Kshetra Kshetrajna Vibhaga YogaChapter 13, Shloka 1 (13.1)

Shankaracharya. kṣatatrāṇāt, kṣayāt, kṣaraṇāt, kṣetravad vā asmin karmaphalaniṣpatteḥ kṣetram iti — why "field"? Because it protects from kshat (injury), because of decay, because of ksharan (perishing), or because, like a field, the fruit of action grows in it; āpādatalamastakaṃ jñānena viṣayīkaroti — the one who makes it, from the soles of the feet to the head, an object of knowledge is the knower of the field.

Acharya Ramanuja. idaṃ śarīraṃ devaḥ aham, manuṣyaḥ aham, sthūlaḥ aham, kṛśaḥ aham iti ātmanā bhoktrā saha sāmānādhikaraṇyena pratīyamānaṃ — "I am a god, I am a human, I am fat, I am thin" — the body appears to be one with the self, but bhoktuḥ ātmanaḥ arthāntarabhūtaṃ tasya bhogakṣetram — it is distinct from the experiencing self; it is that self's field of experience.

Shridhara Swami. He explains the purpose of the chapter: in 12.7 the Lord had said teṣām ahaṃ samuddhartā — I am the one who lifts up My devotees; and na cātmajñānaṃ vinā saṃsārād uddharaṇaṃ saṃbhavati — without knowledge of the Self, deliverance from samsara is not possible; therefore prakṛtipuruṣavivekādhyāya ārabhyate — the chapter on discerning prakriti from purusha begins. And the two prakritis of 7.4–7.5 are here called the field and the knower of the field.

Madhusudana Saraswati. He gives a map of the Gita's structure: the first six chapters give the meaning of "tvam" (you — the individual soul), the middle six that of "tat" (That — Ishvara), and the last six are vākyārthaniṣṭhaḥ — about the oneness of the two. His opening invocation is also famous: let the yogis see the attributeless light if they will; asmākaṃ tu … kālindīpulinodare kim api yan nīlaṃ maho dhāvati — for us, may that blue radiance running along the banks of the Yamuna be the wonder of our eyes.

Madhvacharya. pūrvoktajñānajñeyakṣetrapuruṣān piṇḍīkṛtya vivicya darśayati — he gathers together knowledge, the knowable, the field and the person spoken of earlier, and shows them one by one.