瑜伽論記 7.445

7.445

初中，謂於所緣乃至諸不淨相者，初觀青瘀，次即捨觀膖脹，次又捨觀膿爛等相，由除境相而起作意，於所緣境數正除遣別境現前，名正加行。

Within the first: regarding "with respect to the focal object, down to all characteristics of impurity," first one contemplates the blue-bruised, next one abandons it to contemplate the swollen, and next one abandons it again to contemplate the festering and other characteristics; because of eliminating the characteristics of the object, attention arises, and repeatedly dispelling correctly with respect to the focal object, a different object appears before one—this is called correct preparatory application.