B.G 4.17
karmaṇohyapi boddhavyaṁ boddhavyaṁ ca vikarmaṇaḥ। akarmaṇaśca boddhavyaṁ gahanā karmaṇo gatiḥ ॥17॥
One needs to grasp the understanding of right action, prohibited actions insight must be grasped, indeed, one needs to grasp the understanding of non-performance actions. The ways of action are truly profound.
Gīta Bhāshya 4.17
'Vikarma' differs from right-action ('karma') and non-action ('akarma'). 'Vikarma' means prohibited action. It is further binding. Gaining insight into ways of karma is crucial for discriminating between them. It is a prerequisite to perceive the lord directly, and to get liberated.
na kevalaṁ tat jñātvā mokṣyase, jñātvaiva ityāśayavānāha - karmaṇa iti। taccoktam–
Just by merely knowing (about the action to be performed) one does not get liberated. Having known, one must also gain insight 'regarding action' is indicated by the verse 'karmaṇa'.
"ajñātvā bhagavān kasya karmākarmavikarmakam। darśanaṁ yāti hi mune kuto muktiśca tad vinā॥"
iti।
O Sage, without gaining insight into the right action, non-action, and prohibited action, How is it possible to gain the direct perception of the lord, and without it how liberation is possible?
-states the testimonial.
akarma karmākaraṇam। karmākarmānyat vikarma niṣiddham। bandhakatvāt। tato vivicya karmādi boddhavyam ityādi। na ca śāpādinā।
'akarma' means non-performance of action. Different from right-action and non-action is 'vikarma', which means prohibited action, as it is further binding. Therefore, discriminate different actions by 'gaining insight' is the intended meaning. It is not about a curse etc. (as explained by other commentaries.)
"kavayo'pyatra mohitāḥ।"
"Even the wise are deluded in these situations."
aśakyaṁ caitat jñātum ityāha - gahaneti ॥17॥
-such expression shows it is almost impossible to know (i.e. gain insight into workings of the actions). Same is indicated by the word 'gahana' which means it is "profound and deep".