Śatapatha Brāhmaṇa ("of a hundred paths") 5.1.4.14

5.1.4.14

atha yannaivāro bhavati | brahma vai bṛhaspatirete vai brahmaṇā pacyante yannīvārāstasmānnaivāro bhavati saptadaśaśarāvo bhavati saptadaśo vai prajāpatistatprajāpatimujjayati

And why it is prepared of wild rice:--Brihaspati is the Brahman (priesthood), and those wild-rice grains are cooked with the Brahman (prayer),--therefore it is of wild rice. It is one of seventeen plates, because Pragâpati is seventeenfold: he thus wins Pragâpati.