The Enchiridion (Version 2) : 17

Remember that thou art an actor in a play, of such a kind as the teacher (author) may choose; if short, of a short one; if long, of a long one: if he wishes you to act the part of a poor man, see that you act the part naturally; if the part of a lame man, of a magistrate, of a private person, (do the same). For this is your duty, to act well the part that is given to you; but to select the part, belongs to another.