[206] Then it occurred to the bhikkhus: "When, indeed, should the rains residence (vassa) be entered upon?" They reported this matter to the Blessed One. "Bhikkhus, I allow the rains residence to be entered upon during the rainy season."
Then it occurred to the bhikkhus: "How many occasions are there for entering the rains residence (vassūpanāyikā)?" They reported this matter to the Blessed One. "Bhikkhus, there are these two occasions for entering the rains residence: the earlier and the later. The earlier is to be entered on the day after the full moon of Āsāḷhī; the later is to be entered a month after the full moon of Āsāḷhī. These, bhikkhus, are the two occasions for entering the rains residence."
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.