Rashi on Exodus 22:26/רש"י על שמות כ״ב:כ״ו

1כי הוא כסותה FOR THAT IS HIS RAIMENT — i. e. his upper garment;

2שמלתו means HIS SHIRT (the שמלה for the skin);

3במה ישכב WHEREIN SHALL HE LIE DOWN — These words are used to include amongst the articles which must be returned to him during the day the couch and its coverings on which he rests during day-time (Mekhilta).