1.1.11-12
स्वर्गे लोके न भयं किञ्चनास्ति न तत्र त्वं न जरया बिभेति। उभे तीर्त्वा अशनायापिपासे शोकातिगो मोदते स्वर्गलोके ॥११॥
In the heavenly world, there is no fear of any kind; there, you are not afflicted by old age. Having crossed both hunger and thirst, one who has transcended sorrow rejoices in the heavenly world.
स त्वमग्निं स्वर्ग्यमध्येषि मृत्यो प्रब्रूहि तं श्रद्दधानाय मह्यम्। स्वर्गलोका अमृतत्वं भजन्ते एतद् द्वितीयेन वृणे वरेण ॥१२॥
O Death, you know that heavenly fire; tell it to me, who is faithful. The heavenly worlds attain immortality through it. This I choose as my second boon.
Bhāṣy 1.1.11-12
Lord Hari, being foremost among all, is associated with the Naciketa fire.
"अग्र्यत्वादग्निनामासौ नाचिकेताग्निगो हरिः॥"
"Lord Hari being foremost and supreme among all fires, is associated with the Naciketa fire."