Sri Aurobindo translates Katha Upanishad, First Cycle, First Chapter, Verses 10 and 11: “Nachiketas speaks: ‘Tranquillised in his thought and serene of mind be the Gautama, my father, let his passion over me pass away from him; assured in heart let him greet me from thy grasp delivered; this boon I choose, the first of three.’ Yama speaks: “Even as before assured in heart and by me released shall he be, Auddalaki Aruni, thy father; sweetly shall he sleep through the nights and his passion shall pass away from him, having seen thee from death’s jaws delivered.’ ”
Yama (the restrainer) represents the law of life as well as death. He sets the limits. We observe that physical life is followed by physical death. It is obviously not the normal process of the law for someone to be physically dead for three days and then return to life. The meaning of this first boon lies in the spiritual realisation that requires the ego to release its hold so that the soul can pass beyond the golden barrier that limits the awareness of the outer personality and prevents the shift to the universal, divine standpoint that signals the spiritual awakening.
Sri T.V. Kapaly Sastry notes: “the real nature of the first boon that Yama bestows upon Nachiketas — the boon, a capacity by which he can come back from the higher plane to the physical with the connection between this and the life beyond established, maintaining the thread of consciousness, for the opening is already made and the passage clear, to use the Vedic phrase. We may note in passing that the Sanskrit phrase sutratma meant to refer to the soul in the subtle body (linga deha), very well answers to the description of soul retaining the thread of the personal consciousness in its journey to the other side of Life and discovering the exit passage to return to the Earth-life. This, then, is the first boon, the initial gain of Nachiketas, which every soul aspiring to relive a fuller life has to win; this is done by completely dying first in order to emerge into the Kingdom of the Keeper of the Law by which the Cosmic existence is preserved, through which one has to ascend the heights of existence above the cycle of life and death to the Eternal Life, Freedom, Immortality.”
There are certain experiences that a seeker may undergo where the ego-personality is confronted with a barrier. The flame of the soul’s aspiration is pushing to pass that barrier to the larger truth of existence. A fear of death rises up at that moment where the ego-personality feels like it is about to die if it goes any further. If it turns back at this moment, the transition does not occur at that time and must await a further opportunity. If it passes the barrier, the attachment to the ego and the life of the world passes away. It is possible to return across the barrier to the world of life, and resume one’s role in the world, changed by the knowledge acquired in the process. This experience matches up precisely with the nature of the first boon granted to Nachiketas, the flame of the soul.
Sri Aurobindo, The Upanishads, Katha Upanishad, pp. 213-241, and Kapali Sastry, Lights on the Upanishads, pp. 104-129