The Prophet (pbuh) said, "During your sleep, Satan ties three knots at the back of your necks. He breathes the following into them, 'The night is long so keep on sleeping.' If the person wakes & praises Allah, then one of the knots is unfastened. And if he performs ablution, the second knot is unfastened. When he prays, all of the knots are unfastened. After that he will be energetic & happy. Otherwise he would get up listless & grouchy."