Jim over at Lutheran Guest has a post on the parallel between how the Israelites were commanded to make their altars and care for their bodies. Since St. Paul says that the body is a Temple or, by extension, the body is an altar and locus of rational sacrifice (cf. Rom 12:1), it would seem fitting that the Old Law would prefigure this mystery. So Jim couples the following passages:
"If you make an altar of stone for me, you shall not build it of cut stones, for if you wield your tool on it, you will profane it." (Ex 20:25)I think Jim has a point here. Using tools on something highlights the fact that man, not God, has fashioned something. (Consider how the original copy of the Ten Commandments had been carved not by a tool but by "the finger of God".) That is why we read "if you wield your tool on it, you will profane it."
"You shall not round off the sides of your heads not harm the edges of your beard. You shall not make any cuts in your body for the dead nor make any tattoo marks on yourselves: I am the LORD." (Lev 19:27-28)
There is only one problem with this theory. The ceremonial rite of circumcision is the ultimate act of "wielding a tool or knife" on your body and yet it is the quintessential rite of the Old Covenant. Perhaps not cutting the hair around the Israelite man's head is a sign that he is circumcised. ("I'm not cut around my head up here because I am cut around down there.") This may fit with the idea that monastic tonsure is a kind of "exposed circumcision" designating that a man is consecrated the Lord (an idea found in the "tonsure" of the Old Covenant Nazirites).