Shatapatha Brahmana 5.2.5.12

5.2.5.12

atha yatsaumyaḥ | carurbhavati yadevāsmā agnirdātā varco dadāti tasminnevaitadantataḥ pratitiṣṭhati yadvai varcasvī karma cikīrṣati śaknoti vai tatkartuṃ tadvarca evaitadupaiti varcasvī sūyā iti no hyavarcaso vyāptyā canārtho 'sti tasya babhrurgaurdakṣiṇā sa hi saumyo yadbabhruḥ

And why there is a pap for Soma;--whatever glory, Agni, the giver, gives him, therein he now finally establishes him; and whatever work he, the glorious, wishes to do, that he is able to do. Thus he thereby attains glory,--thinking, 'May I be consecrated, endowed with glory!' for the inglorious one has no concern with success. A brown bull is the fee for this (offering); for such a brown one is of Soma's nature.