Śatapatha Brāhmaṇa ("of a hundred paths") 5.3.2.4

5.3.2.4

atha maitrābārhaspatyaṃ caruṃ nirvapati | hvalati vā eṣa yo yajñapathādetyeti vā eṣa yajñapathādyadayajñiyānyajñena prasajatyayajñiyānvā etadyajñena prasajati śūdrāṃstvadyāṃstvanmitrābṛhaspatī vai yajñapatho brahma hi mitro brahma hi yajño brahma hi bṛhaspatirbrahma hi yajñastatpunaryajñapathamapipadyate so 'pipadyaiva yajñapathaṃ dīkṣate tasmānmaitrābārhaspatyaṃ caruṃ nirvapati

Thereupon he prepares a pap for Mitra and Brihaspati. For verily he who departs from the path of the sacrifice stumbles; and he does indeed depart from the path of the sacrifice, when he puts those unworthy of sacrifice in contact with the sacrifice, and he does indeed now put those unworthy of sacrifice--either Sûdras or whomever else--in contact with the sacrifice. And the path of the sacrifice is Mitra and Brihaspati; for Mitra is the Brahman, and the Brahman is the sacrifice; and Brihaspati is the Brahman, and the Brahman is the sacrifice. Thus he, returns again to the path of the sacrifice; and as soon as he has returned to the path of the sacrifice he is consecrated: therefore he prepares a pap for Mitra and Brihaspati.