瑜伽論記 7.516

7.516

於奢摩他品者乃至於內修受心法觀者，以聞心取彼六想內略俱行四蘊，名修內受心法觀，攝心住於六想名為內略，受等非色四蘊體相無雜故名無亂，亦可定之境故名無亂。

From "Regarding the side of calm abiding... up to ...inwardly cultivating the contemplation of feelings, mind, and dharmas": taking the four aggregates that run concurrently with the inward condensation of those six contemplations through the hearing mind is called cultivating the internal contemplation of feelings, mind, and dharmas. Withdrawing the mind to abide in the six contemplations is called inward condensation. Because the substance and marks of the four non-material aggregates such as feeling are unmixed, it is called non-distraction; alternatively, because it is the domain of concentration, it is called non-distraction.