Śatapatha Brāhmaṇa ("of a hundred paths") 1.8.3.19

1.8.3.19

athāgnīdāhānuprahareti | tadyatrāsyetara ātmāgaṃstadevāsyaitadgamayetyevaitadāha tūṣṇīmevānuprahṛtya cakṣuṣpā agne 'si cakṣurme pāhītyātmānamupaspṛśati teno apyātmānaṃ nānupravṛṇakti

The Âgnîdhra says (to the Adhvaryu), 'Throw (the single stalk) after (the prastara)!'--'whither his (the sacrificer's) other self went, thither make it now go,' this is what he thereby says. [The Adhvaryu] having thrown it silently after, touches himself, with the text (Vâg. S. II, 16 f): 'Guardian of the eye art thou, O Agni; guard mine eye!' In this way also he does not throw himself into the fire after (the prastara or sacrificer).