Shatapatha Brahmana 7.2.2.6

7.2.2.6

sa dakṣiṇamevāgre yunakti | atha savyamevaṃ devatretarathā mānuṣe ṣaḍgavam bhavati dvādaśagavaṃ vā caturviṃśatigavaṃ vā saṃvatsaramevābhisampadam

He yokes the right (ox) first, then the left one: thus it is (done) with the gods, differently in human (practice). It is a team of six oxen, or one of twelve oxen, or one of twenty-four oxen: it is the year (he obtains) as the consummation.