俱舍論疏 14.100

14.100

論「重說晝夜為半月等」，此通伏難。難云：若唯有二分齊，何故經中云「或半月或一月受近住戒」？通云：說半月等者，此說重受日夜戒，滿半月等名半月等，非是一受經半月等也。如《無量壽經》云「日日如是受王八戒」，即是日日受，經半月等也。

The treatise says: "Repeatedly declaring a day and night amounts to half a month, and so forth." This resolves a latent objection. The objection asks: If there are only two limits, why does the sūtra state, "receiving the upavāsa precepts for half a month or for one month"? The resolution states: mentioning half a month and so forth refers to repeatedly receiving the day-and-night precepts, completing half a month and so forth being named "half a month and so forth"; it does not mean that a single reception spans half a month or the like. Just as the Amitāyus Sūtra says, "Thus day after day receiving the royal eight precepts," it means receiving them day by day, spanning half a month and so forth.