Śatapatha Brāhmaṇa ("of a hundred paths") 13.7.1.2

13.7.1.2

sa vā eṣa sarvamedho daśarātro yajñakraturbhavati daśākṣarā virāḍvirāḍu kṛtsnamannaṃ kṛtsnasyaivānnādyasyāvaruddhyai tasminnagnim parārdhyaṃ cinoti paramo vā eṣa yajñakratūnāṃ yatsarvamedhaḥ parameṇaivainam paramatāṃ gamayati

Now this Sarvamedha is a ten-days’ (Soma-) sacrifice, for the sake of his gaining and winning every kind of food, for the Virâg consists of ten syllables, and the Virâg is all food. At this (sacrifice) he builds the greatest possible fire-altar, for this--to wit, the Sarvamedha--is supreme amongst all sacrificial performances: by means of the supreme (sacrifice) he thus causes him (the Sacrificer) to attain supremacy.