俱舍論疏 12.139

12.139

「論曰至中劫末起」，明起時也。此諸災患由二為本，謂耽異食及性懶墮。由此煩惱，故劫漸減，有小三災。

On "The Śāstra says ... arise at the end of an intermediate kalpa": Explaining the time of their arising. These various calamities have two things as their root: namely, indulgence in alien tastes and an innate indolence. Due to these afflictions, the kalpa gradually decreases and the three minor calamities occur.