Chapter 8 - Verse 4

अधिभूतं क्षरो भावः पुरुषश्चाधिदैवतम् ।
अधियज्ञोऽहमेवात्र देहे देहभृतां वर ॥ ४ ॥

adhibhūtaṃ kṣaro bhāvaḥ puruṣaścādhidaivatam .
adhiyajño’hamevātra dehe dehabhṛtāṃ vara .. 4 ..


The physical region (Adhibhūta) is the perishable existence, and Puruṣa or the Soul is the divine region (Adhidaivata). The Adhiyajña (Entity concerned with Sacrifice) is Myself, here in the body, O best of the embodied.
Read the commentary

The Adhibhūta is that which gathers itself round the whole animated creation and is composed of the whole perishable existence, i.e., of every thing that has birth.

Puruṣa is, literally, that by which every thing is filled, (pri=to fill) or that which lies in the body (pur), i.e., the Hiraṇyagarbha, the Universal Soul abiding in the Sun (Āditya), the Sustainer and the Stimulator of the sense-organs of all living beings.

The Adhiyajña is He who identifies himself with all acts of sacrifice, the Deity named Viṣṇu; the sruti says: “Yajña (Sacrifice) is verily Viṣṇu” (Taittiriya-Samhita, 1-7-4). He is verily Myself. I am the Deity concerned with all acts of sacrifice in the body.—As an act of sacrifice (yajna) has to be performed by the body, it is said to be inherent in it, and as such it may be said to rest in the body.