The hair is the very outermost part of the body, and "hair" in the Bible represents the outermost expression of whatever the body represents. In most cases, the hair and beard are discussed in connection with prophets and other holy men. Since they represent the Lord as He is expressed through the Bible, their hair and beards represent the literal, external stories of the Bible -- which is why they were forbidden to shave or clip their hair. In other cases, the hair and beard can represent the external truths a person uses to live, the day-to-day ideas. Very often, the hair and beard are connected with power and strength in the Bible, Samson being the most obvious example. This is because the whole power of the Bible, in all its depth and meaning, is contained within those literal stories we read. If we disregard the stories, then we will cut ourselves off from the power of the Bible, the same way Samson lost his strength when Delilah cut his hair. This is also why calling someone "bald" was considered a great insult, why shaving the heads of captives was a way to humiliate them, and why people would shave their own heads as either a sign of mourning or as a sign of transition a new level of understanding -- removing the old external ideas so new ones can grow in their place. "Hair" can also be used in the negative, to represent the falsities that can guide someone in an evil life.