B.G 4.18

karmaṇyakarma yaḥ paśyedakarmaṇi ca karma yaḥ। sa buddhimān manuṣyeṣu sa yuktaḥ kr̥tsnakarmakr̥t ॥18॥

He who sees non-action in activities, and sees action in non-activities is the knowledgeable among humans, and he is rightly engaged in Yōga and performs all the right actions.

Gīta Bhāshya 4.18

The person who perceives non-action in action thinks, "Indeed, I am only reflecting what is presented to my consciousness. Vishnu is the one who is performing the actions, not me." Person who perceives action in non-action thinks - 'This indeed is the Supreme Lord who always performs activities such as creation and so on'. 'buddhimān' - knowledgeable. 'yukto' - engaged in Yōga. 'kr̥tsnakarmakr̥' - indicates he alone gets all-encompassing results.

karmādisvarūpamāha - karmaṇīti।

The verse 'karmaṇi' describes the essence and nature of action.

karmaṇi kriyamāṇe sati akarma yaḥ paśyet 'viṣṇoreva karma nāhaṁ citpratibimbaḥ kiñcit karomi' iti।

When action is being performed, one who perceives non-action, thinks - 'Indeed, Vishnu only is doing the actions, not I. I am only reflecting what my consciousness presents to me.'

akarmaṇi suptyādau akaraṇāvasthāyāṁ parameśvarasya karma yaḥ paśyati 'ayameva parameśvaraḥ sarvadā sarvasr̥ṣṭyādi karoti' iti।

When in the state of non-action such as sleep and so on, one who perceives the actions of the Supreme Lord, thinks - 'This indeed is the Supreme Lord who always performs activities such as creation and so on'.

sa buddhimān jñānī । sa eva ca yukto yogayuktaḥ। sarvākaraṇāt sa eva ca kr̥tsnakarmakr̥t kr̥tsnaphalatvāt ॥18॥

He is 'buddhimān', means he is knowledgeable. Such a person only is 'yukta', means he is engaged in Yōga. Because of absence of all self driven actions, such a person alone is 'kr̥tsnakarmakr̥', i.e. performs all right actions, which means, he alone gets all-encompassing results.