俱舍論疏 14.220

14.220

論「諸持律者言至彼飲酒故」，敘異說也。佛既唯除性罪，皆開供病比丘。既復有病，佛不開酒，故知飲酒是性罪攝。第一證也。

The treatise states: "Vinaya masters say: [...] because of their drinking alcohol." This recounts a dissenting view. Since the Buddha allowed everything for sick monks with the sole exception of natural offenses, and yet when there was illness the Buddha did not allow alcohol, one knows therefore that drinking alcohol is subsumed under natural offenses. This is the first proof.