سنن أبي داود

Abu Hurairah reported the Messenger of Allah (May peace be upon him) as saying: when any of you goes to his bed, he should dust his bedding with the inner extremity of his lower garment, for he does not know what has come on it since he left it. He should then lie down on his right side and say: In Thy name, my mercy on it, but if Thou lettest it go, guard it with that which Thou guardest Thy upright servants.