四分律行事鈔資持記 1.1262

1.1262

受日中。此謂七月九日受者。下引文證。疏云：如律所制，及七日還；今限明相，乃在界外；絕此分齊，故說破夏；又云：七月十日受七日，至第七日是夏滿，不來無犯。（準知從十已去受者，前緣未竟，不來奔夏。）

Under "accepting days": this refers to accepting them on the ninth day of the seventh month. Below, texts are cited as evidence. The commentary states: as regulated by the Vinaya, one must return within seven days; now, when the dawn light appears, one is outside the boundary; having severed this limit, it is therefore called breaking the rains retreat. It also states: accepting seven days on the tenth day of the seventh month, until the seventh day the rains retreat is complete; not returning incurs no offense. (One should know accordingly that for those accepting from the tenth onward, if the prior business is not finished, they do not rush back for the rains retreat.)