佛說目連問戒律中五百輕重事經 1.80

1.80

問：「夏中幾日得結坐？」答：「從四月十六日盡五月十五日，日日可結，此謂坐初。有事難不得結，或五三四日乃至一月盡，不失前坐，此名三十日結坐一日受歲。後坐人唯得一日結坐。過七月十五日，有事難日日可受歲，盡八月十五日，此名一日結坐三十日受歲。」

Question: "During the summer, on which days may one establish the retreat?" Answer: "From the sixteenth day of the fourth month through the fifteenth day of the fifth month, one may establish it on any day; this is called the beginning of the retreat. If there are obstacles and difficulties and one cannot establish it, whether after three, four, or five days up to the end of a month, one does not lose the earlier retreat; this is called 'thirty days to establish the retreat, one day to receive monastic age.' Those of the later retreat may only establish the retreat on a single day. Past the fifteenth day of the seventh month, if there are obstacles and difficulties, one may receive monastic age on any day, up to the fifteenth day of the eighth month; this is called 'one day to establish the retreat, thirty days to receive monastic age.'"