Brahma Sutras – According to Shankara 1-1-9
Topic 9 - The word Prāṇa to be understood as Brahman
अत एव प्राणः ॥ २३ ॥
ata eva prāṇaḥ || 23 ||
ata eva—For the same reason; praṇaḥ—(the word) Prāṇa (refers to Brahman).
23. For the same reason (the word) ‘Prāṇa’ (also refers to Brahman).
“‘Which is that deity?’ ‘Prāṇa,’ he said.
For all these beings merge in Prāṇa alone and from Prāṇa they arise” (Chh. 1. 11. 4-5).
The question is whether Prastava (a division of Sāman) is a symbol of the vital force or Brahman.
Here Prāṇa does not mean the vital force but Brahman, in which sense it is used in texts like, “The Prāṇa of Prāṇa” (Brih. 4. 4. 18). Why?
Because the characteristic of Brahman, “All these beings merge in Prāṇa,” etc. is mentioned.
All the Jīvas merge in Prāṇa, and that is possible only if ‘Prāṇa’ is Brahman and not the vital force (the ordinary sense of the word), in which only the senses get merged in deep sleep.