Śatapatha Brāhmaṇa ("of a hundred paths") 4.2.5.19

4.2.5.19

idaṃ vā apūpamaśitvā kāmayate | dhānāḥ khādeyaṃ karambhamaśnīyāṃ dadhyaśnīyāmāmikṣāmaśnīyāmiti te sarve kāmā yā yajñasya devatāstāḥ suprītā asannityatha yadeṣā prātaḥsavana eva maitrāvaruṇī payasyāvakLptā bhavati netarayoḥ savanayoḥ

For, when one has eaten cake here, he wishes, 'I should like to take parched grains, I should like to eat porridge, I should like to eat sour curds, I should like to eat clotted curds!' All these (are Objects of one's) wishes: it is in order that those who are the deities of the sacrifice shall be well-pleased. Now as to why that offering of clotted curds (payasyâ) is prepared only at the morning libation, and not at the two other libations (Soma feasts).