Sayyiduna Abu Hurairah (may Allah be pleased with him) narrated that the Messenger of Allah (peace and blessings of Allah be upon him) said: Satan ties three knots at the back of the head of any one of you when he sleeps, and on each knot he breathes the following words: "The night is long, so sleep." Then if one wakes up and remembers Allah, one knot is undone; and when he performs ablution, the second knot is undone; and if he prays (obligatory or voluntary prayer), then the third knot is undone. Thus, in the morning, he becomes energetic and good-natured; otherwise, he becomes lazy and of bad disposition.