B.G 18.18

ज्ञानं ज्ञेयं परिज्ञाता त्रिविधा कर्मचोदना। करणं कर्म कर्तेति त्रिविधः कर्मसङ्ग्रहः ॥१८॥

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 Bhāshya 18.18

The term 'karma saṅgrahaḥ' in the context means 'collection of causes of actions'.
The hypothesis that recommended injunctions and moral rules have no effect on sentient beings because of the non-agency, similar to inert insentient things, is refuted. A sentient being differs from an insentient because of its intentionality (apekṣya), which arises from knowledge, the object of knowledge and the knower. Even in inaction, the egoistic sense of doership, i.e. intentionality is involved. Even when one is not the doer, desires arise by the grace of God, instrumented, based on the stated causes (knowledge, the object of knowledge, and the knower) through the method, and the benevolent human goal is achieved through actions.

एवं तर्हि न पुरुषं अपेक्ष्य विधिः। अकर्तृत्वात् इत्यत आह - ज्ञानं इति॥

Then, if it is postulated, that the rule does not dependent on a person due to non-agency, it is contradicted by the verse 'jñānaṃ', i.e. 'knowledge'.

त्रिविधा कर्मचोदना। एतत् त्रिविध मपेक्ष्य कर्मविधिः इति त्रिविधा उच्यते। कारणानि सङ्क्षिप्याह - करणं इति॥

The impulse to action is threefold (viz knowledge, the object of knowledge, and the knower). Considering this threefold impulse, the procedure of how action come about is described as threefold (instrument, action, and the doer). The causes (five types stated earlier) are summarized here as 'karaṇaṃ' i.e. the instrument.

कर्म सङ्ग्रहः कर्मकारणसङ्ग्रहः। अधिष्ठानादि करणे एव अन्तर्भूतः। तथाहि ऋग्वेदखिलेषु -

The term 'karma saṅgrahaḥ' in the context means 'collection of causes of actions'. Earlier indicated 'adhiṣṭhāna' i.e. body and others, are indeed included in the term 'instrument'. Hence, it is stated in Rigvedakhila:

"ज्ञानं ज्ञेयं ज्ञानिनं चाप्यपेक्ष्य विधिरुत्थितः। करणं चैव कर्ता च कर्मकारणसङ्ग्रहः॥"

"From 'knowledge, the knowable, and the knower' comes forth the intentionality governed by the methods and rules. The instrument and the doer are collectively the cause of actions."

इति।

- stated thus.

अकर्तृत्वेपि विधिद्वार ईश्वरप्रसादात् इच्छोत्पत्त्या उक्त कारणैः कर्मद्वारा पुरुषार्थो भवतीति। ईश्वराधीनत्वेपि विधिद्वारा नियतः तेनैव। यदि च इच्छादिः जायते तर्हि कारितमेव ईश्वरेण। फलं च नियतम्। वस्तुतो अकर्तृत्वेपि अभिमानिकं कर्तृत्वं तस्यैव। स्वातन्त्र्यं च जडमपेक्ष्येव इति न प्रवृत्तिविधि वैयर्थ्यम्। सर्वं चैतत् अनुभवोक्तप्रमाणसिद्धं इति न पृथक् प्रमाणमुच्यते ॥१८॥

Even when one is not the doer, desires arise by the grace of God, instrumented, based on the stated causes (Knowledge, the object of knowledge, and the knower) through the method, and the benevolent human goal is achieved through actions. These depend on God alone, operated by Him through the governing methods. If desires arise, then they are indeed caused by God. The results are also obtained through governing principles. In reality, even in non-doership, the egoistic sense of doership, i.e. intentionality, is involved which comes under His governance. Indeed, independence (of the sentient agent) is significant in comparison to the insentient due to its intentionality, and thus the injunction (to act) is not futile. All this is established by experiential evidence, and thus separate evidence is not required.