tat kṣetraḿ yac ca yādṛk ca
yad-vikāri yataś ca yat
sa ca yo yat-prabhāvaś ca
tat samāsena me śṛṇu

Translation of Bhagavad Gita 13.4

Now please hear My brief description of this field of activity and how it is constituted, what its changes are, whence it is produced, who that knower of the field of activities is, and what his influences are.

Commentary by Sri A.C. Bhaktivedanta Swami Prabhupada of Gaudiya Sampradaya:

The Lord is describing the field of activities and the knower of the field of activities in their constitutional positions. One has to know how this body is constituted, the materials of which this body is made, under whose control this body is working, how the changes are taking place, wherefrom the changes are coming, what the causes are, what the reasons are, what the ultimate goal of the individual soul is, and what the actual form of the individual soul is. One should also know the distinction between the individual living soul and the Supersoul, their different influences, their potentials, etc. One just has to understand this Bhagavad-gita directly from the description given by the Supreme Personality of Godhead, and all this will be clarified. But one should be careful not to consider the Supreme Personality of Godhead in every body to be one with the individual soul, the jiva. This is something like equating the potent and the impotent.

Commentary by Sri Vishvanatha Chakravarthi Thakur of Gaudiya Sampradaya:

Now the Lord begins to elaborate on what he has said previously in abbreviated form.

Hear from me in brief of what the body consists (yac ca) – a conglomeration of five gross elements, prana, senses and other things; what qualities it exhibits (yadrk)- such as desire; what its transformations are (yad vikari)–being subject to changes either favorable or unfavorable; from what it arises (yatah)–from the combination of matter and soul; by what it is distinguished (yat)–by differences among various moving or non-moving bodies; and who (yah) is he (sa)–the knower of the field – the jiva and the paramatma.

The neuter form singular yat and tat are used instead of the masculine, though jiva, paramatma and the field are referred to, by the rule of grammar napumsakam anapumsakennaikavac ca (Panini 1.2.69). If there is a group of items with the same base of various genders including neuter, the neuter gender can be used to indicate all of them. This operation is called eka sesa (single remainder).

Commentary by Sri Ramanuja of Sri Sampradaya:

13.4 What the ‘Field is’ namely, what its substance is; what it is ‘like’, namely, what things depend on it; what its ‘modifications’ are, namely, what its transformations are; what the ‘purpose’ is for which it has been originated; ‘what it is,’ namely, what its true nature is; ‘who it is,’ namely, who the individual self is and what Its nature is like; what Its ‘powers’, are, namely, what powers It possesses. All this, briefly learn from Me.

Commentary by Sri Sridhara Swami of Rudra Sampradaya:

Here prakriti or the material substratum pervading physical existence which has 24 categories consisting of the mind, ego, five organs of perception, the five senses, etc.is specifically meant by the word ksetra or the field of activity. Yet since the non-distinctiveness of matter as I and mine is evolved as such only in the physical body, in order to differentiate from it this body is called the ksetra. To clarify in further detail Lord Krishna proposes to explain what the ksetra referred to by Him is in itself such as inert, of the nature of its object, etc. What is it like such as possessed of qualities such as desire and aversion. What are its modifications such as which senses is it endowed with. How does it arise meaning how is it in conjunction with prakriti and the brahman. What is its form and how is it directed to be either sentient or insentient in just one of innumerably unlimited varieties of species. Also what is the ksetrajna or knower of the ksetra in reality and what power does it have by virtue of its transcendental and inconceivable majesty by the potency it is endowed with. All these things Lord Krishna will now explain in brief.

Commentary by Sri Madhvacharya of Brahma Sampradaya:

What the yad viktri of the ksetra means what are its transformations and by what modifications is it affected. Yatas ca yat means by Him the Supreme Lord the ksetra has originated and that it is He alone who energized it. The words sa ca ya specifies the Supreme Lord also and indicates His form.

Now begins the summation.

The words yatas ca yat indicates that solely by the energy of the Supreme Lord all creation is energized. He is the sole energizer. Prerana means having similarity in thoughts. Sometimes even dialogue is called samvad similar talk. Since Lord Krishna energizes all creation He also energizes the thoughts of all and sometimes such thoughts manifest which are similar to His own. This is natural. So He is known as anusarini or anusmanta the ordainer of thoughts which have divine origins in Him. The ksetrajna is the atma or eternal soul and is upadrishta or the witness with supra-natural connecting abilities for thoughts and things divine which emanate from the Supreme Lord and induces this in those who seek self-realisation of the atma and attainment of the ultimate consciousness. Lord Krishna infers that this can be known is by its effect.

Commentary by Sri Keshava Kashmiri of Kumara Sampradaya:

Now Lord Krishna explains in brief the true nature of the ksetra the field of activity and the ksetra-jna the knower of the field. The relationship the ksetra has with the ksetra-jna and the consciousness which is established in Him. Knowledge of the ksetra means what type entity is embodied and the qualities are what modifications restricts it and what is its means of evolving itself through the interrelationship of matter and spirit. And of the ksetra-jna exactly what is the atma or eternal soul, who is the knower of the ksetra and what is its powers and potencies.

Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:

13.4 Srnu, hear, i.e., having heard, understand; me, from Me, from My utterance; samasena, in brief; about (all) tat, that-the true nature of the field and the Knower of the field, as they have been described; as to yat, what; tat, that-tat stands for that which has been indicated as ‘This body’ (in verse 1); ksetram, field is, which has been referred to as ‘this’; ca, and; yadrk, how it is along with its own qualities; yadvikari, what its changes are; ca, and; yatah, from what cause; arises yat, what effect (-arises is understood-); sah ca yah, and who He, the Knower of the field indicated above, is; ca, and; yat-prabhavah, what His powers are. Yat-probhavah is He who is possessed of the powers arising from the adjuncts. The word ca has been used (throughout) in the sense of and. For making the intellect of the hearer interested the Lord praises that true nature of the field and the Knower of the field which is intended to be taught:

Commentary by Sri Abhinavagupta of Kaula Tantra Sampradaya:

13.4-5 Tat Ksetram etc. Rsibhih etc. Why it modifies : due to what this [Field] suffers modification. Collectively : not at all separately (one by one). [The Bhagavat] decides all the questions in a general way. Of course, many a time in many a way this has been declared by the seers and by the scritpures. But, let Me (the Bhagavat) explain this collectively (briefly).

Sanskrit Shloka Without Transliteration Marks:

tat ksetram yac ca yadrk ca
yad-vikari yatas ca yat
sa ca yo yat-prabhavas ca
tat samasena me srnu

Sanskrit to English Word for Word Meanings:

tat — that; kṣetram — field of activities; yat — what; ca — also; yādṛk — as it is; ca — also; yat — having what; vikāri — changes; yataḥ — from which; ca — also; yat — what; saḥ — he; ca — also; yaḥ — who; yat — having what; prabhāvaḥ — influence; ca — also; tat — that; samāsena — in summary; me — from Me; śṛṇu — understand.