मृत्युप्रोक्तां नचिकेतोऽथ लब्ध्वा विद्यामेतां योगविधिं च कृत्स्नम् । ब्रह्मप्राप्तो विरजोऽभूद्विमृत्यु- रन्योऽप्येवं यो विदध्यात्ममेव ॥ १८॥

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English Translation

Having received this wisdom taught by the King of Death and the entire process of yoga, Nachiketa became free from impurities and death and attained Brahman. Thus it will be also with any other who knows, in this manner, the inmost Self. 

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English Commentary

This conclusion of the story intended to eulogise knowledge is now stated. Nachikêtas having obtained from Death by the granting of boons, the knowledge of the Brahman imparted as above said and also all the instruction about yôga with its fruits, attained Brahman, i.e., became immortal. How? Being already freed from vice and virtue and from desire and ignorance. Not merely Nachikêtas alone but even another who like Nachikêtas, knows the âtman and realizes its true nature unconditioned and within all, and not its form which is not within all. Who knows the nature of the âtman, as thus stated, such knower also; ‘being untainted becomes deathless, by attaining Brahman’ should be supplied to complete the sentence.

Sri Shankaracharya