Sayyiduna Anas (may Allah be pleased with him) narrates: I have seen the companions (may Allah be pleased with them) of the Noble Prophet (peace and blessings be upon him); they would be made to stand for prayer, to the extent that sometimes I would even hear some of them snoring, but then they would get up and perform the prayer and would not perform ablution again. The narrator named Ibn Mubarak stated this: "According to us, this ruling is when they would fall asleep while sitting." This hadith is authentic.