俱舍論疏 14.104

14.104

論「必應有法至一晝夜故」，有部答也。法性微細唯佛能知。經中既說唯一晝夜，故應有法能為障礙。

The treatise says: "There must surely be a dharma ... because [the sūtra specifies] only one day and night." This is the Sarvāstivādin's answer. The nature of dharmas is subtle and known only to the Buddha. Since the sūtra explicitly speaks of only one day and night, there must be a dharma capable of acting as an obstacle.