From Sahih Bukhari (Hadith 6320):
Narrated Abu Huraira:The Prophet (ﷺ) said, "When anyone of you go to bed, he should shake out his bed with the inside of his waist sheet, for he does not know what has come on to it after him, and then he should say: 'Bismika Rabbi Wada`tu Janbi wa bika arfa'uhu, In amsakta nafsi farhamha wa in arsaltaha fahfazha bima tahfazu bihi ibadakas-salihin
Reference: Bukhari 6320