俱舍論疏 28.179

28.179

論「下七皆然至無由生故」，述下七地皆具離染及生，有上地故。有頂唯一，無上地故，不可說生。

The passage of the śāstra from 'The lower seven are all likewise...' down to '...because there is no condition for rebirth' explains that the lower seven stages all possess detachment from defilement and rebirth, because higher stages exist above them. The Summit of Existence has only one, because there is no higher stage above it, so one cannot speak of rebirth [into a higher stage].