It was narrated from Bara' bin 'Azib that

the Prophet (saas) said to a man: "When you go to lay down, or go to your bed, say: Allahumma aslamtu wajhi ilayka, wa al-ja'tu zahri ilayka, wa fawwadtu amri ilayka, raghbatan wa rahbatan ilayka, la malja'a wa la manja'a minka illa ilayka, amantu bi kitabikal-ladhi anzalta, wa nabiyyikal arsalta [O Allah, I have submitted my face (i.e., myself) to You, and I am under Your command (i.e., I depend upon You in all my affairs), and I put my trust in You, hoping for Your reward and fearing Your punishment. There is no fleeing from You and no refuge from You except with You. I believe in Your Book that You have revealed and in Your Prophet whom You have sent).' Then if you die that night, you will die in a state of the Fitrah (nature), and if you wake in the morning you will wake with a great deal of good."