大毘盧遮那成佛經疏 13.47

13.47

Now, although empty space has no characteristics and is unobstructed, it cannot accomplish great affairs. Now, although this emptiness of the Tathāgata has nothing to rely upon, it can accomplish all supreme affairs; surpassing that empty space, it cannot be rivaled. The essence of great compassion is the Tathāgata's eye. This eye is born from great compassion and can generate great compassion (inquire further into this).