Śatapatha Brāhmaṇa ("of a hundred paths") 2.6.1.35

2.6.1.35

athāsya puroḍāśasyāvadāya | savye pāṇau kurute dhānānāmavadāya savye pāṇau kurute manthasyāvadāya savye pāṇau kurute

Thereupon he takes one 'cutting' from the cake and puts it in his left hand; from the parched grain also he takes one cutting and puts it in his left hand; and from the porridge also he takes one cutting and puts it in his left hand.