Śatapatha Brāhmaṇa ("of a hundred paths") 11.4.1.2

11.4.1.2

kaurupañcālo vā ayam brahmā brahmaputraḥ yadvai no'yamardhaṃ na paryādadīta hantainam brahmodyamāhvayāmahā iti kena vīreṇeti svaidāyaneneti śaunako ha svaidāyana āsa

'This fellow is a Kurupañkâla Brahman, and son of a Brahman--let us take care lest he should deprive us of our domain: come, let us challenge him to a disputation on spiritual matters.'--'With whom for our champion?'--'With Svaidâyana.' Svaidâyana, to wit, was Saunaka.