Mishkat al-Masabih #573

Abu Sa'id said: We observed the prayer after nightfall with God’s Messenger, and he did not come out till about half the night had passed. He then said, “Take your places,” and when we had done so 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 the sickness of the sick, I would delay the prayer till half the night had gone;” Abu Dawud and Nasa’i transmitted it.