असक्तबुद्धिः सर्वत्र जितात्मा विगतस्पृहः।नैष्कर्म्यसिद्धिं परमां संन्यासेनाधिगच्छति॥
asakta-buddhiḥ sarvatra jitātmā vigata-spṛhaḥnaiṣkarmya-siddhiṃ paramāṃ sannyāsenādhigacchati
Word by word
The verse says
Whose understanding is unattached everywhere, who has mastered himself, whose wanting has gone: by letting go he reaches the highest fulfilment, where action no longer binds.
In plain words
A summary of where all of this arrives.
Unattached everywhere. Self-mastered. Wanting gone.
And the state is called naiṣkarmya - freedom from the binding of action. Not freedom from action. He is still doing things. They no longer stick.
Where you've felt this · in growing older
Your father's friend is seventy-three and still runs the small business he started, three days a week. He is much better company than he was at fifty, when he worked constantly and the business was the same size. Nothing about the work has changed. He stopped needing it to prove anything, and the work got easier.
Going deeper
Freedom from the binding of action, rather than from action itself, is the distinction this whole book has been building towards.
Naiṣkarmya is easily misread as inactivity, and the tradition itself has sometimes read it that way. But 18.11 already closed that door: nobody with a body can stop acting. So what the word has to mean is action that leaves no residue.
The three conditions given are the mechanism. Unattached understanding means the mind is not gripping the outcome. Self-mastery means the senses are not deciding what happens next. Wanting gone means there is nothing the action is secretly for.
And the thing worth noticing is that the person described is not less effective. Nothing here suggests withdrawal. It describes someone doing the same things with far less of himself caught in them, which is why it tends to show up as lightness rather than as absence.