Judging something wrongly by what I would call "reading the book by its cover" is prejudice. Human beings will judge us according to our physical appearance,race,tribe,religion, financial status, education and the like. But God looks at our hearts. He goes beyond the what man can see. Samuel used his physical eyes to judge, when God wanted to choose a king for Israel. God tells him in 1 Samuel 16:7 that he doesn't judge like men. People would often look at someone's stature or physical appearance to make conclusions about their character which is not authentic.