Priests must not make bald spots on their heads, shave off the edges of their beards, or make cuts in their bodies.
It was before appointed that the priests should teach the people the statutes God had given concerning the difference between clean and unclean, Lev 10:10, Lev 10:11. Now here it is provided that they should themselves observe what they were to teach the people. Note, Those whose office it is to instruct must do it by example as well as precept, Ti1 4:12.
Commenting on Leviticus 21:1-9
They shall not make baldness upon their head,.... For the dead, as Jarchi, Aben Ezra, and Ben Gersom; not shave their heads, or round the corners of them, or make baldness between their eyes on that account; as those things were forbid the Israelites, so the priests also; this and what follow being superstitious customs used among the Heathens in their mournings for the dead...
They shall not make baldness upon their heads . . . nor . . . cuttings in their flesh--The superstitious marks of sorrow, as well as the violent excesses in which the heathen indulged at the death of their friends, were forbidden by a general law to the Hebrew people (Lev 19:28).