Ammar bin Razayq عمار بن رزيق · General Behavior (Kitab Al-Adab)

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.

I came to Ibn ‘Umar when he set his slave free. He took a stick or something else from the earth and said; for me there is no reward even equivalent to this. I heard the Messenger of Allah (May peace be upon him) say: If anyone slaps or beats his slave the atonement due from him is to set him free.