維摩經玄疏 2.103

2.103

第二、辨一心三觀者，正是圓教利根菩薩之所修習。所以者何？不思議心因緣之理，甚深微妙，其觀慧門難解難入。今明此一心三觀，亦為三意：一，明所觀不思議之境；二，明能觀三觀；三，明證成。

Second, discerning the threefold contemplation in a single mind: this is precisely what is cultivated by bodhisattvas of sharp faculties in the perfect teaching. Why is this so? The principle of causes and conditions of the inconceivable mind is extremely profound and subtle, and its gate of contemplative wisdom is difficult to understand and difficult to enter. Now, clarifying this threefold contemplation in a single mind also has three points: first, clarifying the inconceivable object of contemplation; second, clarifying the threefold contemplation that is able to contemplate; third, clarifying the verification and attainment.