瑜伽師地論略纂 11.95

11.95

論云「是染、非染，耎、中、上品」者，以犯罪時，有品階降，故云耎、中、上也。

The Treatise states: '[whether] it is defiled or undefiled, soft, middling, or superior'; this is because when committing an offense, there are graded ranks, and so it says soft, middling, and superior.