Musnad Ahmad 30:190

Sufyan narrated to us, from Abu al-Zinad, from al-A'raj, from Abu Hurairah, from the Prophet (peace and blessings of Allah be upon him): "Satan ties three knots upon the nape of the neck of one of you. At every knot, he strikes: 'You have a long night, so sleep'—and he said once: 'He strikes upon him at every knot: a long night.' He said: 'If he wakes up and remembers Allah, the Mighty and Majestic, one knot is untied. If he performs ablution, two knots are untied. If he prays, the knots are untied, and he wakes up in the morning with a good soul and energetic. Otherwise, he wakes up in the morning with a foul soul and lazy.'"