Маджхима Никая 3:7
SUJATOTena kho pana samayena bhagavā tadahuposathe pannarase pavāraṇāya puṇṇāya puṇṇamāya rattiyā bhikkhusaṅghaparivuto abbhokāse nisinno hoti.
Now, at that time it was the sabbath—the full moon on the fifteenth day—and the Buddha was sitting surrounded by a Saṅgha of monks for the invitation to admonish.