19. yatha dipo nivatastha
ne 'ngate sa 'pama smrta
yunjato yogam atmanah
(19) As a lamp in a windless place flickereth not, to such is likened the yogi of subdued thought who practises union with the Self (or discipline of himself)
The yogi's thought is absorbed in the Atman. Fleeting glimpses or passing visions should not be confused with the insight into Atman which is the one safeguard against all delusions.
20. yatro 'paramate cittarn
yatra cal 'va 'tmana 'tmdnam
pasyann atmam tusyati
(20) That in which thought is at rest, restrained by the practice of concentration, that in which he beholds the Self through the self and rejoices in the Self ;
21. sukham atyantikam yat
tad buddhigrahyam atindriyam
vetti yatra na cai 'va yarn
sthitas calati tattvatah
(21) That in which he finds this supreme delight, perceived by the intelligence and beyond the reach of the senses, wherein established, he no longer falls away from the truth;
See Katha Up., III, 12 While the Supreme is beyond perception by the senses, it is seizable by reason, not by the reason which deals with sense data and frames concepts on their basis but reason which works in its own right. When it does so, it becomes aware of things not indirectly, through the medium of the senses or the relations based on them, but by becoming one with them. All true knowledge is knowledge by identity. Our knowledge through physical contact or mental symbols is indirect and approximate. Religion is contemplative realization of God.
22. yam labdhva ca 'param labham
manyate na 'dhikam tatah
yasmin slhito na duikhsna
guruna 'pi vicalyale
(22) That, on gaining which he thinks that there is no greater gain beyond it, wherein established he is not shaken even by the heaviest sorrow;
23. tat vidyad duhkhasarhyoga-
viyogarh yogasamjmtam sa
(23) Let that be known by the name of yoga, this disconnection from union with pain. This yoga should be practised with determination, with heart undismayed.
In verses 10--22 the intense fixation of the mind on its object with a view to liberation is taught. It is the repose of the liberated spirit in its own absoluteness and isolation. The self rejoices in the Self. It is the kaivalya of the Sãrhkhya purua, though, in the it, it becomes identified with blessedness in God.
nirvinnacetasa: nirvedarahitena cetasa. . We must practise yoga without slackness of effort arising from the thought of prospective pain.