Musnad Abu Ya'la al-Mawsili 109:299

Ibn Numayr narrated to us, my father narrated to us, from al-A‘mash, from Abu Sufyan, from Jabir, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "There is no Muslim man or Muslim woman, male or female, who sleeps at night except that there is a knotted rope upon his head. If he wakes up and remembers Allah, one knot is untied. If he then stands, performs ablution, and prays, all of his knots are untied, and he wakes up energetic, having attained goodness. But if he sleeps without remembering Allah, he wakes up with his knots upon him, heavy."