If, as in a dream, you see a light brighter than the sun, your remaining attachments will suddenly come to an end and the nature of reality will be revealed. Such an occurrence serves as the basis for enlightenment. But this is something only you know. You can't explain it to others. Or if, while you're walking, standing, sitting, or lying in a quiet grove, you see a light, regardless of whether it's bright or dim, don't tell others and don't focus on it. It's the light of your own nature. Of if, while you're walking, standing, sitting, or lying in the stillness and darkness of night, everything appears as though in daylight, don't be startled. It's your own mind about to reveal itself. Or if, while you're dreaming at night, you see the moon and stars in all their clarity, it means the workings of your mind are about to end. But don't tell others.
Source: The Zen Teaching of Bodhidharma, p. 33
Contributed by: Zaady