Midrasch zu Wajikra 21:5

1) (Vayikra 21:5) ("They shall not make a baldness upon their head, and the corners of their beard they shall not shave off, and in their flesh they shall not cut any cutting.") "They shall not make a baldness": I might think that (even) if he made four or five bald spots he would be liable for one alone; it is, therefore, written "a baldness," to stipulate liability for each one individually.

2) "upon their head": What is the intent of this? Because it is written (Devarim 14:1) "Do not lacerate yourselves and do not make baldness between your eyes for the dead," I might think that only "between the eyes" entails liability. Whence is the head included? From "upon their head," to include (all of) the head.

3) I might think that (only) with Cohanim, to whom Scripture relegated additional mitzvoth, is there liability for each bald spot and for the head as well as between the eyes, but with Israelites, where this does not obtain, there is liability there for one bald spot only, and only for "between the eyes." It is, therefore, written "baldness" (here, in respect to Cohanim). "baldness" (there, in respect to Israelites), to create an identity (gezeirah shavah), viz.: Just as with Cohanim there is liability for each bald spot and for the head as well as for between the eyes, so, with Israelites. And just as with Israelites liability for (creating) baldness obtains only vis-à-vis the dead, so, with Cohanim.