Bhagavad Gita · Karma YogaChapter 3, Shloka 15 (3.15)

Shankaracharya — from the Veda to the Supreme Self. The udbhava of action — its source, that which reveals it — is the Veda (the Veda tells us what is to be done). The Veda came forth from the akṣara — the imperishable Supreme Self — puruṣa-niḥśvāsavat — like a person's breath, effortlessly. Since the Veda illumines all meanings, it is sarvagata (all-pervading); and since its main subject is the rules of yajña, it is nityaṃ yajñe pratiṣṭhitam — ever established in yajña. That is, the root of the wheel ultimately reaches the Supreme Self.

Acharya Ramanuja — the body and the individual self. Here "brahma" is a transformation of prakriti — the body. He gives evidence: in the Mundaka (1.1.9), tasmād etad brahma nāma rūpam annaṃ ca jāyate — here "brahma" means prakriti; and in Gita 14.3, mama yonir mahad brahma. Therefore: action arises from the body; and the body becomes fit for action when presided over by the akṣara — the individual self (the self nourished by food and drink). Sarvagataṃ brahma = sarvādhikārigataṃ śarīram — the body of all who are eligible — nityaṃ yajñe pratiṣṭhitam — is ever founded on yajña (because the body comes from food, food from rain, rain from yajña).