Text:

स त्वमग्निँ स्वर्ग्यमध्येषि मृत्यो प्रब्रूहि त्वँ श्रद्दधानाय मह्यम् ।
स्वर्गलोका अमृतत्वं भजन्त एतद्द्वितीयेन वृणे वरेण ॥ १३ ॥

sa tvamagnim̐ svargyamadhyeṣi mṛtyo prabrūhi tvam̐ śraddadhānāya mahyam |
svargalokā amṛtatvaṃ bhajanta etaddvitīyena vṛṇe vareṇa || 13 ||

13. Oh Death! thou knowest the fire which leads to heaven; explain to me who am zealous that (the fire) by which those, whose world is heaven, attain immortality. I pray for this by my second boon.

Shankara’s Commentary:

The fire, which helps one to attain the heaven possessed of such attributes, thou, Oh Death! knowest; and as thou knowest, teach me who am zealous by which fire sacrificing, men attain heaven and immortality or become Devas. This knowledge of the fire, I crave by my second boon.