BhG 18.18

syntax

jñānam (knowledge) jñeyam (object of knowledge) parijñātā [iti] (the knower) tri-vidhā karma-codanā [asti] (there is a threefold impetus to activities).
karaṇam (the instrument) karma (activity) kartā iti (a doer) tri-vidhaḥ karma-saṅgrahaḥ [asti] (there is a threefold constitution of activities).

grammar

jñānam	–	jñāna 1n.1 n. – knowledge, wisdom, intelligence (from: √jñā – to know, to understand);
jñeyam	–	jñeya (√jñā – to know, to understand) PF 1n.1 n. – to be known, to be learnt;
parijñātā	–	parijñātṛ 1n.1 m. – the knower (from: pari-√jñā – to distinguish, to perceive, to understand);
tri-vidhā	–	tri-vidha 1n.1 f. – threefold, of three parts (from: tri – three; vi-√dhā – to divide, vidhā – division, part);
karma-codanā	–	karma-codanā 1n.1 f.; TP: karmaṇāṁ codaneti – the impetus to activties (from: √kṛ – to do, karman – activity and its result; √cud – to impel, to incite, to accelerate, codanā – impetus, rule, direction);
karaṇam	–	karaṇa 1n.1 n. – deed, the instrument, helper, a sense organ (from: √kṛ – to do);
karma	–	karman 1n.1 n. – activity (from: √kṛ – to do);
kartā	–	kartṛ 1n.1 m. – a doer (from: √kṛ – to do);
iti	–	av. – thus (used to close the quotation);
tri-vidhaḥ	–	tri-vidha 1n.1 m. – threefold, of three parts (from: tri – three; vi-√dhā – to divide, vidhā – division, part);
karma-saṁgrahaḥ	–	karma-saṁgraha 1n.1 m.; TP: karmaṇāṁ saṅgraha iti – constitution of activities (from: √kṛ – to do, karman – activity and its result; sam-√grah – to hold together, to support, saṁ-graha – holding together, collection, protection);

textual variants

karma-codanā → karma-vedanā / karma-nodanā (knowledge of activity / the impetus to activities);
karaṇaṁ → kāraṇaṁ / trividhaṁ (cause / threefold);
karma-saṅgrahaḥ → karma-saṁśrayaḥ / karma-saṁgrahaṁ (refuge for activities / constitution of activities);

Śāṃkara

athedānīṃ karmaṇāṃ pravartakam ucyate—
jñānaṃ jñāyate’neneti sarva-viṣayam aviśeṣeṇocyate | tathā jñeyaṃ jñātavyam, tad api sāmānyenaiva sarvam ucyate | tathā parijñātā upādhi-lakṣaṇo’vidyā-kalpito bhoktā | ity etat trayam eṣām aviśeṣeṇa sarva-karmaṇāṃ pravartikā tri-vidhā tri-prakārā karma-codanā | jñānādīnāṃ hi trayāṇāṃ saṃnipāte hānopādānādi-prayojanaḥ sarva-karmārambhaḥ syāt | tataḥ pañcabhir adhiṣṭhānādibhir ārabdhaṃ vāṅ-manaḥ-kāyāśraya-bhedena tridhā rāśī-bhūtaṃ triṣu karaṇādiṣu saṃgṛhyate ity etad ucyate—karaṇaṃ kriyate’neneti bāhyaṃ śrotrādi, antaḥ-sthaṃ buddhyādi, karma īpsitatamaṃ kartuḥ kriyayā vyāpyamānam, kartā karaṇānāṃ vyāpārayitopādhi-lakṣaṇa iti tri-vidhas tri-prakāraḥ karma-saṃgrahaḥ | saṃgṛhyate’sminn iti saṃgrahaḥ, karmaṇaḥ saṃgrahaḥ karma-saṃgrahaḥ | karmaiṣu hi triṣu samavaiti, tenāyaṃ tri-vidhaḥ karma-saṃgrahaḥ

Rāmānuja

sarvam idam akartṛtvādyanusandhānaṃ sattvaguṇavṛddhyaiva bhavatīti sattvasyopādeyatājñāpanāya karmaṇi sattvādiguṇakṛtaṃ vaiṣamyaṃ prapañcayiṣyan karmacodanāprakāraṃ tāvad āha
jñānam kartavyakarmaviṣayaṃ jñānam, jñeyaṃ ca kartavyaṃ karma, parijñātā tasya boddheti trividhā karmacodanā / bodhaboddhavyaboddhṛyukto jyotiṣṭomādikarmavidhir ityarthaḥ / tatra boddhavyarūpaṃ karma trividhaṃ saṃgṛhyate karaṇaṃ karma karteti / karaṇam sādhanabhūtaṃ dravyādikam; karma yāgādikam; kartā anuṣṭhāteti

Śrīdhara

hatvāpi na hanti na nibadhyate ity etad evopapādayituṃ karma-codanāyāḥ karmāśrayasya ca karma-phalādīnāṃ ca triguṇātmakatvān nirguṇasyātmanas tat-sambandho nāstīty abhiprāyeṇa karma-codanāṃ karmāśrayaṃ cāha – jñānam iti | jñānam iṣṭa-sādhanam etad iti bodhaḥ | jñeyam iṣṭa-sādhanaṃ karma | parijñātā evambhūta-jñānāśrayaḥ | evaṃ trividhā karma-codanā | codyate pravartyate ‚nayā iti codanā | jñānādi-trayaṃ karma-pravṛtti-hetur ity arthaḥ | yad vā codaneti vidhir ucyate | tad uktaṃ bhaṭṭaiḥ – codanā copadeśaś ca vidhiś caikārtha-vācina iti | tataś cāyam arthaḥ ukta-lakṣaṇaṃ triguṇātmakaṃ jñānādi-trayam avalambhya karma-vidhiḥ pravartate iti | tad uktaṃ traiguṇya-viṣayā vedā iti | tathā ca karaṇaṃ sādhakatamam | karma ca kartur īpsitatamam | kartā kriyā-nirvartakaḥ | karma saṅgṛhyate ‚sminn iti karma-saṅgrahaḥ | karaṇādi trividhaṃ kārakam | kriyāśraya ity arthaḥ | sampradānādi kāraka-trayaṃ tu parasparayā kriyā-pravartakam eva kevalam | na tu sākṣāt kriyāyāṃ āśrayaḥ | ataḥ karaṇādi-trayam eva kriyāśraya ity uktam |

Viśvanātha

commentary under the verse BhG 18.19

Baladeva

jñāna-kāṇḍavat karma-kāṇḍe ‚pi jñānādi-trayam asti | tac ca saniṣṭhena karmaṭhena bodhyam iti upadiśati jñānam iti | jñānaṃ jñeyam parijñātety evaṃ trika-yuktā karma-codanā jyotiṣṭomādi-karma-vidhiḥ codanā copadeśaś ca vidhiś caikārtha-vācina ity abhiyuktokteḥ | tat trikaṃ svayam eva vyākhyāti karaṇam iti | yaj jñānaṃ tat karaṇaṃ jñāyate ‚nena iti nirukteḥ karaṇa-kārakam ity arthaḥ | yaj-jñeyaṃ kartavyaṃ jyotiṣṭomādi tat karma-kārakam | yas tu tasya parito ‚nuṣṭhānena jñātā, sa karteti kartṛ-kārakam | evaṃ karma-saṅgraho jyotiṣṭomādi karma-vidhis trividhaḥ karaṇādi-kāraka-traya-sādhyaś codanā-saṅgraha-śabdayor aikyārthaḥ