Śatapatha Brāhmaṇa ("of a hundred paths") 1.5.2.7

1.5.2.7

sa yadāśrāvayati | yajñamevaitadanumantrayata ā naḥ śṛnūpa na āvartasvetyatha yatpratyāśrāvayati yajña evaitadupāvartate 'stu tatheti tenopāvṛttena retasā bhūtenartvijaḥ sampradāyaṃ caranti yajamānena paro 'kṣṃ yathā pūrṇapātreṇa sampradāyaṃ careyurevamanenartvijaḥ sampradāyaṃ caranti tadvācaivaitatsampradāyaṃ caranti vāgghi yajño vāgu hi retastadetenaivaitatsampradāyaṃ caranti

Now when he (the Adhvaryu) calls (on the Âgnîdhra), he thereby calls after the sacrifice, 'Listen to us! come back to us!' and when he (the Âgnîdhra) responds, then the sacrifice comes back, saying 'so be it!' and with it, thus passing over to them, as with seed, the priests carry on the tradition, imperceptibly to the sacrificer; for even as people hand on from one to the other a full vessel, in the same way they (the priests) hand down that (sacrifice) from one to the other. They hand it down by means of speech, for the sacrifice is speech (prayer), and speech is seed: therefore they keep up the tradition by means of it.