瑜伽師地論略纂 1.60

1.60

覺有三緣。「不勝疲極」者，睡經多時，便置困頓，自然覺悟，名不勝疲睡極故。言「有所作要期事」者，將有所作，發願要期，求後覺故。總以心、心所為性。

Awakening has three conditions. "Unable to withstand extreme fatigue" means that after sleeping for a long time, exhaustion sets in, and one naturally awakens; it is called being unable to withstand the extreme point of tiring sleep. "Having an appointed task to be done" means that when one is about to undertake a task, one makes a vow and an appointment, seeking a later awakening. In general, it takes the mind and mental factors as its nature.