俱舍論記 26.56

26.56

「掉心者至能治彼故」者，第七對掉心、不掉心。能治彼故，即是定心。故《婆沙》云「不掉心者，謂善心奢摩他相應故。」或能治彼，即是行捨。故《婆沙》云「不掉心者，謂善心行捨相應故。」

Regarding "The restless mind ... because it can counteract that": this is the seventh pair, restless mind (auddhatya-citta) and non-restless mind. That which can counteract that is the concentrated mind. Thus the Mahāvibhāṣā says: "The non-restless mind refers to the wholesome mind because it is associated with calm abiding (śamatha)." Or, that which can counteract that is equanimity in application (upekṣā). Thus the Mahāvibhāṣā says: "The non-restless mind refers to the wholesome mind because it is associated with equanimity in application."