kaTha Upanishad
अतिमुच्य धीराः प्रेत्यास्माल्लोकादमृता भवन्ति ॥ — 1.2, kena Upanishad.
[Meaning: The wise, having relinquished all false identifications, become immortal upon departing from this world.]
The kena Upanishad tells us that “A dead man becomes immortal after death.”
At first glance, what the kena says appears to be a paradox: it suggests that one must “depart” to become immortal. If we take this literally, it sounds as though a dead man becomes immortal — yet a dead man is no longer there to experience immortality. This apparent contradiction is the gateway to a deeper Vedantic truth.
kena Upanishad is actually pointing to a “solution” for the one thing we all struggle with: Freedom from the constant, grinding cycle of birth, death, and the misery in between — what the shAstra-s (texts) call samsAra.

On the insistent questioning of the highly determined Naciketas, Lord Yama had no alternative but to reveal the secret code to ending the transient mortal world and realizing the “immortality” that one actually and already is. It is not some thing new that one acquires. It is prAptasya prAptiH (