न हि ज्ञानेन सदृशं पवित्रमिह विद्यते।तत्स्वयं योगसंसिद्धः कालेनात्मनि विन्दति॥
na hi jñānena sadṛśaṃ pavitramiha vidyatetatsvayaṃ yogasansiddhaḥ kālenātmani vindati
Word by word
The verse says
There is nothing in this world as clean as knowing. Whoever has come to completeness in the practice finds it in himself, in time.
In plain words
A superlative, and then a very patient promise.
Nothing here is as pavitram — pure, purifying — as knowing.
And then the qualifier that stops it being a slogan: kālena — in time, in due course. Nobody is promised this on Tuesday.
Where you've felt this · in health
You do the exercises for a year and nothing changes. Then one ordinary morning you climb the stairs without thinking about it.
Going deeper
Two words are worth separating here.
Pavitra is ritual vocabulary — that which purifies, makes fit for use. The Gita has been steadily transferring ritual language to inner states since 3.9, and this is the completion of that move. The purifier is not the water or the fire. It is seeing.
Kālena is the honest half. Everything in this chapter about fire and boats could read as instantaneous. This says it takes as long as it takes.
And svayam ātmani vindati — he finds it himself, in himself. After 4.34 sent Arjuna to a teacher, this says the actual finding happens internally and by him.
Those two are not in conflict. The teacher points; nobody can do the seeing on your behalf. The Gita holds both without resolving them into a single instruction, which is more useful than either alone.