Yajur Veda, Katha Upanishad, Part One, Chapter II, 12,13

 The wise man who, by means of concentration on the Self, realises that ancient, effulgent One, who is hard to be seen, unmanifest, hidden and who dwells in the buddhi and rests in the body-he, indeed, leaves joy and sorrow far behind.

Yajur Veda, Katha Upanishad, Part One, Chapter II, 12

The mortal who has heard this and comprehended it well, who has separated that Atman, the very soul of dharma, from all physical objects and has realised the subtle essence, rejoices because he has obtained that which is the cause of rejoicing. The Abode of Brahman, I believe, is open for Nachiketa.

Yajur Veda, Katha Upanishad, Part One, Chapter II, 13