俱舍論疏 22.186

22.186

論「既唯勝解至唯是有漏」，述唯有漏所以。無漏行相，十六行也。非是勝解作意相應，既唯勝解，明非無漏。

The treatise says, "Since it is solely resolve... it is solely with-outflows," which states the reason why it is solely with-outflows. The undefiled modes of activity are the sixteen modes of activity. They are not associated with mental application of resolve; since it is solely resolve, it is clear that it is not undefiled.