Shatapatha Brahmana 5.5.1.12

5.5.1.12

atha ya eṣa bārhaspatyaścarurbhavati | tasya śitipṛṣṭho gaurdakṣiṇaiṣā vā ūrdhvā bṛhaspaterdiktadeṣa upariṣṭādaryamṇaḥ panthāstasmācitipṛṣṭho bārhaspatyasya dakṣiṇā tam brahmaṇe dadāti bṛhaspatirvai devānām brahmaiṣa vā etasya brahmā bhavati tasmāttam brahmaṇe dadāti sa haitenāpi viṣṭhāvrājyannādyakāmo yajeta tadasmintsarvato 'nnādyaṃ dadhāti sa hānnāda eva bhavati

And what pap there is for Brihaspati, the fee for that is a white-backed bullock; for to Brihaspati belongs that upper region, and above that there is that path of Aryaman: therefore a white-backed (bullock) is the fee for the Brihaspati (pap). He gives it to the Brahman, for Brihaspati is the Brahman of the gods, and this one is his (the Sacrificer's) Brahman: therefore he gives it to the Brahman. Even a vishthâvrâgin who is desirous of food may perform this offering: he (the priest) thereby bestows food upon him from all quarters, and verily he becomes an eater of food.