What did the Prophet Muhammad (saw) say was the result of a person performing ablution before they go to sleep?
 Abu Huraira transmitted it from the Apostle of Allah (may peace be upon him):                      When any one of you goes to sleep, the devil ties three knots at the back of his neck, sealing every knot with:" You have a long night, so sleep." So if one awakes and mentions Allah, a knot will be loosened; if he performs ablution two knots are loosened; and if he prays (all) knots will be loosened, and in the morning he will be active and in good spirits; otherwise we will be in bad spirits and sluggish in the morning.