俱舍論疏 18.49

18.49

論「餘無間罪至恩等少故」，明餘逆輕、重次第。「第五」，謂出佛身血。「第三」，謂殺阿羅漢。「第一」，謂殺母。「第二」，謂殺父。「恩等少故」者，釋漸輕所以。

The Śāstra states: "The remaining anantarya offenses... because gratitude and so forth are lesser", explaining the sequence of gravity among the other anantaryas. "The fifth" refers to shedding the Buddha's blood. "The third" refers to slaying an arhat. "The first" refers to killing one's mother. "The second" refers to killing one's father. "Because gratitude and so forth are lesser" explains the reason why they become progressively lighter.