From Tenzin Chogyel’s The Life of the Buddha.
The Bohisattva remained with five ascetics, and together they undertook renunciation at the top of Mount Gaya. While they lived there the Bodhisattva had a flash of insight and developed three metaphors for the experience of awakening that no one had heard before:
A piece of driftwood that is soaking wet will not catch fire no matter how much it is rubbed. Just so, the body and the mind that are dowsed in desire are unable to reach liberation.
Even if the driftwood is only moist this will still be the case. Just so, even if the body is kept apart from desire, if the mind is not kept apart, one remains unable to reach liberation.
Only a dry stick is able to catch fier. Just so, body and mind must be well separated from desire.