यः पूर्वं तपसो जातमद्भ्यः पूर्वमजायत । गुहां प्रविश्य तिष्ठन्तं यो भूतेभिर्व्यपश्यत । एतद्वै तत् ॥

ॐ

English Translation

He verily knows Brahman who knows the First-born, the offspring of austerity, created prior to the waters and dwelling, with the elements, in the cave of the heart. This, verily, is That. 

ॐ

English Commentary

This shows that he who was pointed as the pratyagâtman and Isvara is the âtman of all. Yah ] some seeker after emancipation. Pûrvam ] first. Tapasah ] from the Brahman defined as knowledge, etc. Jâtam ] created or produced, the first-born of Brahman, i.e., Hiranyagarhha. ‘Born before whom’ is explained. Adbhyah pûrvam ] before the five elements, including water; not before water alone; ajâyata ] was born. This first-born who having created the bodies of the Dêvâs, etc., entered the âkâs of the heart of every living thing and is there seated, perceiving sounds, etc., Bhûtêbhih means Bhûtâh or elements in the nature of cause and effect. Who sees him seated with them: who sees thus. See this alone, i.e., Brahman the subject of our present discussion.

Sri Shankaracharya