जानाम्यहँ शेवधिरित्यनित्यं न ह्यध्रुवैः प्राप्यते हि ध्रुवं तत् ।
ततो मया नाचिकेतश्चितो’ग्निरनित्यैर्द्रव्यैः प्राप्तवानस्मि नित्यम् ॥ १० ॥

jānāmyaham̐ śevadhirityanityaṃ na hyadhruvaiḥ prāpyate hi dhruvaṃ tat ।
tato mayā nāciketaścito’gniranityairdravyaiḥ prāptavānasmi nityam ॥ 10 ॥

10. I know that the treasure is uncertain; for, that which is constant is never reached by things which change. Therefore, has Nachiketa fire been propitiated by me with the perishable things, and I have attained the eternal.

Shankara’s Commentary:

Delighted, Death says again: I know that the treasure, i.e., the reward of Karma, because it is sought after like a treasure, is not eternal; for, that which is constant, i.e., the treasure named Paramatman cannot be reached by things not constant. That treasure alone, which is in the nature of uncertain happiness, can be obtained by uncertain things. Therefore, by me, though I know that the eternal cannot be attained by ephemeral aids, has been propitiated, the fire Nachiketas leading to the attainment of heavenly joys with ephemeral things. By virtue of that, I have attained the position of authority, this office of Death known as Svarga eternal, but only relatively.