The Grand Ayatollah Safi answered questions about the situation in the month of Ramadhan when a person knows that if falls sleep, nocturnal emission will happen.
Question: One hour is left to dawn’s call to prayer (Adhan), and the person knows that if falls sleep, does not wake up until call to prayer and nocturnal emission will happen; can the person sleep or not? And if the person sleeps and nocturnal emission happens, and call to prayer is performed, is the fasting correct or not?
The Grand Ayatollah Safi: If the mentioned person knows that before dawn’s call to prayer will have nocturnal emission, according to Wajeb precaution must not sleep.
source : Shafaqna