四分律行事鈔資持記 1.980

1.980

第二。即約中齋以分前後。又但制前，後皆通故。所以不釋晝夜者，既制侵早，日夕可知故。律中，恐明相現，開略說戒，則通夜明矣。

The second [passage] divides before and after based on the midday meal. Furthermore, because it only regulates before [the meal], after [the meal] is universally permissible. The reason day and night are not explained is that, since the early morning is prescribed, evening can be inferred. In the Vinaya, fearing that the morning light might appear, an exception is granted to abbreviate the recitation of the precepts, which makes it clear that this applies throughout the night.