Authentic Supplication Number 025.

Upon going to his bed each night, the Messenger of Allah would bring his palms together. Then he would spittle (45) in them, then he would recite into them Qul huwal 'allahu 'ahad, Qul 'a`outhu birabbil falaqi, and Qul 'a`outhu birabbin-nasi (46), then he would wipe with them whatever he is able to of his body, he would begin with his head and face, and the foreside of his body. He would do this three times".

Footnotes.
(45) Spittle is being used for the Arabic word nafth. Nafth is to put the tip of your tongue between your lips and to blow lightly as you pull your tongue back which in this case causes a misty spray onto your hands.
(46) Meaning the last three suwar of the Qur'an.

Reporters.
Agreed upon by Bukhari and Muslim, and Al-Albani included it in The Authentic of Good Sayings as #25.