Similar concepts in Kathopanishad and Bhagavd-Gitä
Many mantras of Kathopanishad have been repeated in the Bhagavad-Gitä with some variation.
‘sarve vedäh yad padam ämananti - - I.2.15
‘na jäyate mryate vä kadäcit- - I.2.18
‘indriyebhyah parä hyarthäh- - I.3.10
‘indriyebhyah param manah - - II.3.7
‘na tatra surya - - II.2.15
‘urdhvamulo’väk-säkhah - - II.3.1
Similar mantras of Katha in various Upanishads
‘na-tatra-suryo bhäti – II.2.15
‘bhayät-asya-tapati – II.3.3
‘bhisäsmad-vätah -- II.8.1
‘iha-ced-asakad – II.3.4
‘äsino duram vrajati – I.2.21
‘tad-ejati - 5
(I would like to believe that mantras of Brhadaranyaka Upanishad are repeated/adapted in other Upanishad, since Brhadaranyaka is an one of the oldest Upanishads. – author)
Rgveda and Kathopanishad
Occurrence of seeds of Upanishadic thoughts are found in the Rgveda. This has been noticed and identified by the scholars. ‘--- Upanishad is later than the Samhitäs, and later than the Brähmanas, but the first germs of Upanishad doctrines go back to at least as far as the Mantra-period, which conservatively has been fixed between 1000 and 800 BCE. Concepts corresponding to the general teaching of the Upanishads occur in certain hymns of the Rgveda-Samhitä, they must have existed therefore before that collection was finally closed.
‘hamsah sucisat - -
Ka. Up. – II.2.2
The famous Sauri-rk (RV-IV.40.5) addressed to Sürya is in the tenth mandala of Rgveda – ‘hamsah-sucishad-vasur-antarikshasad-hotä vedishad-atithir-duronasat—.‘This famous mantra is repeated in Sukla-Yajurveda-X.24, XII.14, SYV-Känvaäakhä-XIII.5.18, XV.6.25, Taittiriya-Samhitä-I.8.15.2, IV.2.1.5, Aitareya-Brähmana-IV.20, Taittiriya-Äranyaka-X.10.2 in toto. It is repeated in Kathopanishad also Ka.Up.-II.2.2., and Mahänäräyana Upanishad – Ma.Nä.Up.- I.2.6.
Mantras proving Reincarnation
Ka.Up.-I.1.6 and II.2.7 are pramäna for the theory/law of incarnation.
Pramäna for concept of Jivanmukti
Ka.Up.-II.2.1 and II 3.14 are pramäna vakyas for the theory/concept of Jivanmukti in Advaita.
Pramäna for Law of Karma
‘---yathäkarma yathäsrutam’. - Ka.Up.-II.2.7
It must have been obvious to the readers, who are acquainted with the paramparä, that the first chapter of Kathopanishad (Valli 1, 2, and 3) are chanted during the funeral, followed by 8th chapter of Bhagavad-Gitä, and Garuda Puräna. This tradition is etched in my memory since, while the Kathopanishad was being taught in the Gurukulam, mother of one of our Trustees departed. We were requested to chant the first chapter of Kathopanishad, followed by 8th chapter of Bhagavad-Gitä. And Sri Vishnusahasranäma at the special request of the lady. None of us knew Garuda Puräna. A selected batch of us, proficient in chanting went to the city and chanted for required 11 or 13 days.
Imagery of the Chariot
Kathopanishad uses the imagery of chariot in its teaching I.3.3 and I.3.4. It compares,
i) the Ätmä, the "Self" is the chariot's passenger
ii) the body is the chariot itself
iii) intellect – buddhi is the chariot driver
iv) the mind - manas is the reins
v) the indriyas – five senses are the chariot horses
vi) the objects perceived by the senses are the chariot's path.
Analogy with Fire, Air and the Sun
II.2.9 – Oneness of Ätmä compared with fire
II.2.10 – Oneness of Ätmä compared with air
II.2.11 – Oneness of Ätmä compared with the Sun
(I.3.14) – Arise, awake – was adapted by Swami Vivekananda. Many are surprised to see the source in the Upanishad.
Mantra I.3.4 – The concept of ‘razor’s edge’ in the Upanishad was popularized by Somerset Maugham in his novel ‘The Razor’s Edge’ in 1944. The novel was later adapted, twice, into films of the same title. The epigraph reads, "The sharp edge of a razor is difficult to pass over; thus the wise say the path to Salvation is hard." taken from a verse in the Ka.Up.- I.3.14. Maugham had visited India in 1938 and met Ramana Maharshi in his ashram.
Explicit mention of Yoga (Meditation and Contemplation)
‘Katha Upanishad’ is also notable for first introducing the term Yoga (lit. "yoking, harnessing") for spiritual exercise,
‘When the five organs of perception become still, together with the mind, and the intellect ceases to be active: that is called the highest state. This firm holding back of the senses is what is known as Yoga. (Ka.Up. II.3.10–11)