大毘盧遮那成佛經疏 2.66

2.66

第三十七「云何鵂鶹心？謂常暗夜思念」者，此鳥於大明中無所能為，夜則六情爽利。若行者晝日雖有所聞，誦習昏憒不得其善巧，至暗夜思憶所為之事，重復籌量便得明了。乃至修禪觀等，亦以暗處為勝。若覺知已，當念等於明暗，令所作意無晝夜之別，是所對治。

The thirty-seventh: "What is the owl mind? It is constantly thinking in the dark night." This bird is powerless in broad daylight, but at night its six faculties are sharp and clear. If a practitioner hears something during the day, reciting and practicing it in confusion without mastering its subtlety, but in the dark night reflects on what was done, weighing it repeatedly and thereby attaining clarity, even regarding the dark as superior for cultivating dhyāna-contemplation and the like; when one realizes this, one should reflect on the equality of light and darkness, making one's mental application free from the distinction of day and night; this serves as its antidote.