成唯識論述記 6.354

6.354

述曰：行者行蘊，行蘊中捨，簡受蘊中捨，故置行言，非謂行也。亦以四法為體，別正對治掉舉，體性靜住為業。

The Commentary states: 'Formative factors' refers to the aggregate of formative factors (saṃskāra-skandha). Equanimity within the aggregate of formative factors is distinguished from equanimity (upekṣā) within the aggregate of sensation (vedanā-skandha); hence the word 'formative' is prefixed, not that it means bodily movement. It also takes the four factors as its entity; it distinctly and directly counters restlessness, and has peaceful abidance in its essential nature as its activity.