Action is produced from Brahma; Brahma is produced from the Imperishable. Therefore, all-pervading Brahma is always in the Sacrifice.
कर्म ब्रह्मोद्भवं विद्धि ब्रह्माक्षरसमुद्भवम्। तस्मात् सर्वगतं ब्रह्म नित्यं यज्ञे प्रतिष्ठितम्॥