This text includes the mantra and the method to be able to recognize the clear light of sleep.
Lama Zopa Rinpoche says that more than half our time alive is spent sleeping, life goes so quickly, so it is very important to explain how to use going to sleep to develop virtue.
It is taught that by reciting this mantra seven times and blowing on the palm of your right hand, if you fall asleep in the posture of a lion and sleep without interruption by other conceptualizing minds, you will recognize the clear light of sleep and quickly realize the meaning of the perfection of wisdom.
"So Lama Tsongkhapa explained to sleep, but to have light sleep so that you can easily wake up in time to practice Dharma again, so that you don’t waste your meaningful life but use it to benefit yourself and all sentient beings. You can see that the purpose of sleeping is totally different. First your sleeping is not to become the cause of the lower realms but to become the cause of the higher realms." - Lama Zopa Rinpoche