Abu Dawud Book 2, Hadith Number 422.
Chapter : Not known.
Narated By AbuSa’id al-Khudri : We observed the prayer after nightfall with the Apostle of Allah (PBUH), and he did not come out till about half the night had passed. He then said: Take your places. We then took our places. Then he said: The people have prayed and gone to bed, but you are still engaged in prayer as long as you wait for the prayer. Were it not for the weakness of the weak and for the sickness of the sick. I would delay this prayer till half the night had gone.