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.

665. That to “set up a covenant” signifies that he would be regenerated, is very evident from the fact that there can be no covenant between the Lord and man other than conjunction by love and faith, and therefore a “covenant” signifies conjunction. For it is the heavenly marriage that is the veriest covenant; and the heavenly marriage, or conjunction, does not exist except with those who are being regenerated; so that in the widest sense regeneration itself is signified by a “covenant.” The Lord enters into a covenant with man when He regenerates him; and therefore among the ancients a covenant represented nothing else. Nothing can be gathered from the sense of the letter but that the covenant with Abraham, Isaac, and Jacob, and so many times with their descendants, was concerned with them personally, whereas they were such that they could not be regenerated; for they made worship consist in external things, and supposed the externals of worship to be holy, without internal things being adjoined to them. And therefore the covenants made with them were only representatives of regeneration. It was the same with their rites, and with Abraham himself, and with Isaac, and Jacob, who represented the things of love and faith. Likewise the high priests and priests, whatever their character, even those that were wicked, could represent the heavenly and most holy priesthood. In representatives the person is not regarded, but the thing that is represented. Thus all the kings of Israel and of Judah, even the worst, represented the royalty of the Lord; and even Pharaoh too, who set Joseph over the land of Egypt. From these and many other considerations-concerning which, of the Lord’s Divine mercy hereafter-it is evident that the covenants so often entered into with the sons of Jacob were only religious rites that were representative.