Ya'la bin Mamlak says that I asked Umm Salama (may Allah be pleased with her) about the night prayer and recitation of the Prophet (peace be upon him), so she said: The Prophet (peace be upon him) would perform the 'Isha prayer and after that pray the voluntary prayers and then go to sleep. The Prophet (peace be upon him) would sleep for as long as he prayed, and he would pray for as long as he slept. Then the end of the Prophet's (peace be upon him) prayer would be at the time of morning.