俱舍論疏 6.125

6.125

論「頗有前生至已彼劣故」，明前已生勝無漏法，非後已生劣無漏因。

The treatise says, "Is there any earlier-arisen [...] because it is inferior?" which clarifies that an earlier-arisen superior undefiled phenomenon is not a cause for a later-arisen inferior undefiled one.