Sunlight. Lamplight.

Once, a Zen Master encountered a visiting monk.  In front of a group, the master asked the monk, “Where do you come from?”  The monk answered, “I am from the Mountain Monastery of Spiritual Light.”  The master said, “In the day we have sunlight, in the night, we have lamplight.  What is Spiritual Light?”  The monk could not answer.

The Master leaned in close to the monk and whispered, “Sunlight.  Lamplight.”