成唯識論掌中樞要 2.127

2.127

善法立少染法立多者，染法曾熏時長，法廣故，多說之。善法起少時促，法略故，少說之。若在佛位，由因廣故，果善無邊，欲令聞者歡喜希求，所以多說。

Regarding why wholesome dharmas are established few in number while defiled dharmas are established in great number: defiled dharmas have perfumed for a long time and their dharmas are extensive, hence they are spoken of extensively. Wholesome dharmas arise infrequently, their duration is brief, and their dharmas are succinct, hence they are spoken of sparingly. If in the Buddha-stage, because the causes are extensive, the resultant wholesome [qualities] are boundless; in order to cause hearers to rejoice and aspire, they are spoken of extensively.