成唯識論述記 5.273

5.273

述曰：「睡眠」若起，必依身、心沈重惛昧，此是內緣。外眾緣力，即是病等，或涼風等。有時暫起，如《對法》論第一末說，即是間斷非相續義。「惡作」雖亦然。而約義別說此第七識所藉緣少，一類無始，簡別不假內緣而起。又言，內執不假外緣而起，簡別外緣，由此緣故無睡眠也。

The Commentary states: When sleep arises, it must depend on heaviness and obscurity of body and mind; this is the internal condition. The power of external conditions refers to illness and the like, or cool breezes and the like. It arises only temporarily at certain times, as stated at the end of the first fascicle of the Abhidharmasamuccaya-vyākhyā; that is, it has the meaning of being interrupted, not continuous. Although remorse is also like this, in terms of distinctive meanings, it is said that this seventh consciousness relies on few conditions, being of one uniform category from beginningless time, thus precluding relying on internal conditions to arise. Furthermore, it says that internal grasping does not rely on external conditions to arise, precluding external conditions; due to these conditions, sleep is absent.