To speak about (religious) knowledge at night
Narrated Ibn `Abbas: I stayed overnight in the house of my aunt Maimuna bint Al-Harith (the wife of the Prophet (sallallahu ‘alaihi wa sallam) ) while the Prophet (sallallahu ‘alaihi wa sallam) was there with her during her night turn. The Prophet (sallallahu ‘alaihi wa sallam) offered the `Isha’ prayer (in the mosque), returned home and after having prayed four rak`at, he slept. Later on he got up at night and then asked whether the boy (or he used a similar word) had slept? Then he got up for the prayer and I stood up by his left side but he made me stand to his right and offered five rak`at followed by two more rak`at. Then he slept and I heard him snoring and then (after a while) he left for the (Fajr) prayer.