Śatapatha Brāhmaṇa ("of a hundred paths") 8.4.2.13

8.4.2.13

tā vā etā daśeṣṭakā upadadhāti | daśākṣarā virāḍvirāḍagnirdaśa diśo diśo 'gnirdaśa prāṇāḥ prāṇā agniryāvānagniryāvatyasya mātrā tāvataiva tadetāni sarvāṇi bhūtāni pāpmano mṛtyo spṛṇoti

These, then, are ten bricks he lays down,--the Virâg consists of ten syllables, and Agni is Virâg (wide-shining); there are ten regions, and Agni is the regions; there are ten vital airs, and Agni is the vital airs: as great as Agni is, as great as is his measure, by so much he thus frees all these creatures from evil, from death.