Śatapatha Brāhmaṇa ("of a hundred paths") 4.6.7.13

4.6.7.13

yajuṣā ha vai devāḥ | agre yajñaṃ tenire 'tharcātha sāmnā tadidamapyetarhi yajuṣaivāgre yajñaṃ tanvate 'tharcātha sāmnā yajo ha vai nāmaitadyadyajuriti

Now with the Yagus the gods first performed sacrifice, then with the Rik, then with the Sâman and in like manner do they now perform the sacrifice. first with the Yagus, then with the Rik, then with the Sâman; for Yagus, they say, is the same as Yagas (worship).