Ch 18, Sh 50 continued-3, Sh 51-52, Bhagawad Gita, Shankar Bhashya

Even to those who hold that knowledge is formless and not cognized by direct perception, cognition of an object is dependent on knowledge. Hence it has to be admitted that knowledge is as immediate as pleasure etc. And this follows also from the impossibility of a desire to know (knowledge). Had knowledge been not self-evident, it could have been sought for like any object of knowledge. And in that case, as a knower seeks to perceive through knowledge such objects of knowledge as pot etc., similarly the knower would have sought to perceive knowledge through another knowledge! But this is not the case. Therefore knowledge is self-revealing, and for the very same reason the knower also is self-revealed. Hence, effort is not needed for knowledge, but only for the removal of the notion of what is not-Self. Consequently, steadfastness in Knowledge is easy of accomplishment.
It is being stated how this supreme consummation of Knowledge is to be attained:
Yuktah, being endowed; buddhya, with an intellect-which is identical with the faculty of determination; visuddhaya, pure, free from maya (delusion); and niyamya, controlling, subduing; atmanam, oneself, the aggregate of body and organs; dhrtya, with fortitude, with steadines; tyaktva, rejecting; visayan, the objects; sabdadin, beginning from sound, from the context it follows that 'rejecting the objects' means rejecting all things which are meant for pleasure and are in excess of those meant only for the mere maintenance of the body; and vyudasya, eliminating; raga-dvesau, attachment and hatred with regard to things which come to hand for the maintenance of the body.
Therefore,
Vivikta-sevi, one who resorts to solitude, is habituated to repairing into such solitary places as a forest, bank of a river, mountain caves, etc.; laghuasi, eats sparingly, is habituated to eating a little-repairing to solitary places and eating sparingly are mentioned here since they are the causes of tranquility of mind through the elimination of defects like sleep etc.; the person steadfast in Knowledge, yata-vak-kaya-manasah, who has speech, body and mind under control. Having all his organs withdrawn thus, dhyana-yoga-parah nityam, one to whom meditation and concentration are ever the highest (duty) meditation is thinking of the real nature of the Self, and concentration is making the mind one-pointed with regard to the Self itself; one to whom these meditation and concentration are the highest (duty) is dhyana-yoga-parah-. Nityam, (ever) is used to indicate the absence of other duties like repetition of mantra etc. Samupasritah, one who is fully possessed, i.e. ever possessed; of vairagyam, dispassion, absence of longing for objects seen or unseen.