B.G 18.18

jñānaṃ jñeyaṃ parijñātā trividhā karmacodanā। karaṇaṃ karma karteti trividhaḥ karmasaṅgrahaḥ ॥18॥

Knowledge, the object of knowledge, and the knower constitute the threefold impulse to action. Correspondingly, instrument, action, and the doer form the threefold aggregate of causes of actions.

Gīta Tātparya 18.18

The term 'saṅgrahaḥ' refers collectively to the five causes. In the term 'karaṇa' i.e. instrument, the physical body is included. By the term 'daiva', the main agency of the God is indicated. By the term 'kartṛ' independent agency is indicated which is threefold. The term 'karma' i.e. action refers to 'ceṣṭā' i.e. various movements.
The Lord is the instigator of all beings' actions, and He alone is the inspiration behind the knower, known, and knowledge. This is because:
Speciality is twofold: one is called particular (how one is special) and the other is difference (how one is different from the other). Self-sufficiency of the Lord is not an indeterminate state, like the speciality of other ordinary entities, which are primarily based on difference. It is driven by the eternality of His innate-nature, which pervades everything. As His innate-nature is eternal, it becomes His speciality as well. (For a layperson, it is suffice to understand that the attributes of God are non-different from Him, because of His special properties, unlike other entities.)

"samprerayiturīśasya karmasvakhilacetanān। jñātṛjñeyajñānarūpā preranā sā sa eva yat॥

"The Lord is the instigator in all beings' actions, and He alone is the inspiration behind the knower, known, and knowledge.

svarūpeṇaiva nityā sā viśeṣātmatayā bhavet। viśeṣo'pi svarūpeṇa nityaśca syād viśeṣataḥ॥

Because of the eternality of innate-nature, it becomes a special entity. As its innate-nature is eternal, that becomes its speciality.

svanirvāhakatā yasmāt nānavasthā viśiṣṭavat। viśeṣyasya viśiṣṭasyāpyabhedepyavivādini॥

Self-sufficiency is not an indeterminate state, as it is like a particularity. Even in the non-difference, the speciality of particularity remains undisputed.

viśeṣo'styeva nātrāsti hi anavasthā kadācana। jñāturanyo'hamiti bhedastasmāt tayoḥ kutaḥ। paśyāmīti viśeṣo'yamidānīṃ me samutthitaḥ॥

Indeed, there is speciality and particularity here, as there is never any indeterminate state. Therefore, how can there be a confusion between 'I' the knower and another? 'I see,' - thus the particularity in me has now arisen.

ityādyanubhavād bhedo na viśeṣyaviśiṣṭayoḥ। viśeṣaṇaṃ tu dvividhaṃ viśeṣākhyaṃ tathetarat। viśeṣamaṇayed yena proktaṃ tena viśeṣaṇam। viśeṣo'pi viśeṣasya svasyaiva gamako bhavet॥"

Thus, from the beginning of experience, there is no difference between the speciality and the particularity. Speciality is twofold: one is called particular, and the other is different. The speciality should lead by which it is said to be a qualification. The speciality should also be the indicator of itself."

ityādi tattvaviveke।

- these are stated in the ancient text of Tattvavivek, i.e. the discrimination of principles.

saṅgrahaḥ pañcakāraṇānāṃ saṅkṣepaḥ। adhiṣṭhānasya karaṇe antarbhāvāt। daivaśabdoditeśvarasyaiva mukhyakartṛtvāt svatantrakartroḥ kartṛśabdenaiva ukteḥ traividhyam। karma ceṣṭā ॥18॥

The term 'saṅgrahaḥ' refers collectively to the five causes. In the term 'karaṇa' i.e. instrument, the physical body is included. By the term 'daiva', the main agency of the God is indicated. By the term 'kartṛ' independent agency is indicated which is threefold. The term 'karma' i.e. action refers to 'ceṣṭā' i.e. various movements.