Katha Upanishad is one of the principal Upanishads and the commentary (Madhva Bhashya) by Madhvacharya is an important text in Hinduism.
Katha Upanishad is related to the Katha or Kathaka branch of Yajur Veda. According to Madhvacharya, Sri Hari is the sole regulator (niyamaka) of all life, both during the present life (samsara bandha) and even thereafter in the state of liberation (moksha). The subtle philosophy of Brahman and His greatness is explained through a dialogue between Yamaraja and Naciketa.
Madhvacharya begins his bhashya with an invocation to Bhagavan Vamana avatar of Srihari Vishnu and the commentary starts from the twelfth mantra. This explains svargagni vidya, the knowledge of sacrifice leading to svarga (heaven). But Madhvacharya explains that svarga does not mean Indraloka as commonly understood, but it actually means the abode of Bhagavan Vishnu.
Nachiketa, being cursed by his father, Vajasrava, arrives at Yamaloka and waits there fasting for three days until the arrival of Yama from his tour. Yamaraja, after his arrival, sees Naciketa and pleased with his devotion, requests him to be calm and asks him to seek three boons. As the first boon, Nachiketa requests Yamaraja that his father Vajasrava should forgive him and receive him with affection when he returns home. As the second boon, Nachiketa requests Yamaraja to teach him the ritual called Ishtika Yajnya and its modalities. Nachiketa, a wise boy, listens to the teachings attentively and repeats the same word for word. Yamaraja, pleased with his performance, presents his valuable necklace. He also declares that henceforth the rituals will be known as Nachiketa Agni. One who performs this ritual thrice will reach the abode of Bhagavan Srihari Vishnu.
For the third boon, according to some commentators, Nachiketa desired to know whether the jiva (self) existed after death or not. Madhvacharya rejects such interpretations, since Nachiketa, being a self, has gone to Yamaloka after death. On the other hand, according to some learned persons, Bhagavan Vishnu regulates the selves after the death of humans in every cycle of birth and death and also after final liberation (mukti dasa). Nachiketa requests Yamaraja to clear this ambiguity and reveal the secrets of Brahmavidya. Yamaraja says that this divine knowledge is so sacred and secret that even gods have not come to any conclusion. Therefore, he diverts Nachiketa’s attention by offering a number of worldly pleasures. He also tries to persuade him to abandon the particular question. Yamraja says – it is true that Bhagavan Vishnu regulates but how He regulates is still unknown to anyone. But Nachiketa, discarding all material temptations insists that the vidya prayed for should be taught to him.
Yamadeva, satisfied with Nachiketa’s urge for divine knowledge, finally agrees to convey the message. He starts with an introductory note on the greatness of Bhagavan Srihari Vishnu. There are two things in the world. One consists of near and dear mundane matters called preyasa. The other one is the supreme knowledge resulting in final liberation of the self, known as sreyasa. Madhvacharya states that the wise utilize the preyasa to get sreyasa.
Bhagavan Srihari is devoid of a material body, yet He resides in every living being. Such an understanding frees one from all worries. He is not only above all sense organs but also regulates the deities governing the sense organs. Yamaraja explains that the knowledge of Brahman is secured by His grace. He chooses the worthy selves and grants them His vision (aparoksha). Brahma Jnana cannot be secured by mere theistic discussions or logical debates but purely by His grace (parama prasada).
Bhagavan Vishnu is the regulator of every jiva not only after death but also after final liberation (mukta-jiva-niyamaka), so one should secure supreme knowledge and grace by controlling one’s senses, following the Vedic code of conduct, Yoga, and meditation. God has in His possession contradictory attributes, yet He is eternal (nitya) and totally independent (sarva-tantra-svatantra). Bhagavan Vishnu is whole in His original form as well as His incarnate forms.
Bhagavan Vishnu is without defect in every way, and hence he is called hamsa. Srihari Vishnu resides in and regulates every jiva and also the jeevothama (prime soul) who, in turn, regulate various deities of the sense organs. Finally, emphasis is laid on noble conduct and morality of persons interested in the spiritual pursuit of brahma jnana (knowledge of the Ultimate).