Abu Huraira reported Allah's Messenger ﷺ as saying, “When 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 a knot will be loosened, and if he prays a knot will be loosened, and in the morning he will be active and in good spirits; otherwise he will be in bad spirits and sluggish in the morning.” (Bukhari and Muslim.)