Musnad Ahmad

It is narrated from Hazrat Anas (may Allah be pleased with him) that once the time for prayer came, so every person who had a house in Madinah got up and went away to relieve himself and perform ablution. Some emigrants remained who had no house in Madinah. A large vessel of water was brought to the service of the Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) placed his hands in it, but the vessel was not spacious enough, so the Prophet (peace and blessings be upon him) placed only four fingers in it and said, "Come near and perform ablution from it." At that time, the blessed hand of the Prophet (peace and blessings be upon him) was in the vessel. So all of them performed ablution from it, and not a single person remained who did not perform ablution, and still the same amount of water remained in it.