‘A’isha said that he, meaning God’s Messenger, would sleep in the early part of the night and keep awake in the latter part. If he then wished intercourse with his wife he satisfied his desire, and then went to sleep. If he was sexually defiled when the first call to prayer was made, he would get up and pour water on it, but if not, he performed the ablution for the prayer and then prayed two rak'as.
(Bukhari and Muslim.)