Can anybody point me to scriptures, commentaries or expositions on that last part of the analogy, involving sleep/dream/wake
Here's the quote and url...
Samsaric existence entails the uncontrollably recurring experience of death, bardo (the in-between state), and rebirth. We can describe the process by which the three happen as changes of subtlety of mental activity.
The Gelug tradition focuses on purifying our future deaths, the ensuing bardos, and our next rebirths. For Gelug, purifying, here, means to eliminate our samsaric existence such that it never recurs – in other words, to achieve a true stopping (true cessation) of it.
A similar process of change in subtlety occurs when we fall asleep.
- With deep sleep, we reach an extremely subtle level of mental activity.
When dreaming, the level of mental activity is slightly grosser, producing subtle appearances.
When we awaken, our mental activity returns to the gross sensory level.