B.G 8.04

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

adhibhūtaṁ kṣaro bhāvaḥ puruṣaścādhidaivatam। adhiyajño'hamevātra dehe dehabhr̥tāṁ vara ॥4॥

The perishable state (kṣaraḥ bhāvaḥ) is called adhibhūta (that which pertains to the physical elements). The cosmic being (puruṣaḥ) is referred to as adhidaivata (the divine principle). I alone am adhiyajña (the principle of sacrifice) here in the body, O best of the embodied beings.

Gīta Bhāshya 8.04

The word 'bhūtāni' means embodied living entities, and that which is meant for their use is called 'adhibhūtam' (the physical or perishable elements). Phrase 'kṣaro bhāvaḥ' refers to objects subject to destruction or perishable entities. Even in the insentient (avyakta), a transformation or change of state (anyathā-bhāva-ākhyah) leading to destruction is inevitable. This has indeed been stated -

"The insentient (avyakta) of the form of actionless space merges completely into the supreme (during final destruction of the universal)."

- stated thus.

"Therefore, O best among the twice-born, the insentient (avyakta) has arisen, possessing the three qualities."

- stated thus as well.

"The distorted transformation (vikāraḥ) is indeed born from the unmanifest, i.e. avyakta."

- stated thus in the Skanda Purāṇa.

The individual being, i.e. 'jīvaḥ', is called 'puruṣaḥ' because it resides in the body, the 'puri'. So is the case with the lord Saṅkarṣaṇa, the form of Brahmā as well (i.e. the lord as well resides in the city of the Body called 'puri', hence he is also called 'purusha'). He, having control over all the deities, is referred to as their lord, and thus is known as 'adhidaivatam', the divine underlying principle. Also, because he commands and rules over all the deities.

Gīta Tātparya 8.04