Musannaf Ibn Abi Shaybah

Hazrat Abu Uthman says that one night the Holy Prophet Muhammad (peace and blessings be upon him) did not come to lead his companions in the Isha prayer until a third of the night remained. Then he came and saw that some people were standing, some were sitting, and some were lying down. He said to them: Since you have been waiting for the prayer, you are in the state of prayer. Among you, those who are standing, sitting, and lying down.