Sunan Abu Dawood, Chapter: Purification (Kitab Al-Taharah)

Abdullah heard his son praying to Allah: O Allah, I ask Thee a white palace on the right of Paradise when I enter it. He said: O my son, ask Allah for Paradise and seek refuge in Him from Hell-Fire, for I heard the Messenger of Allah (peace_be_upon_him) say: In this community there will be some people who will exceed the limits in purification as well as in supplication.