Leviticus 21

"‘They shall not make any bald place on their heads, nor shall they shave the edges of their beards nor make any cuttings in their flesh." v.5

Read chapter 21.
This chapter is talking specifically to the priests and their conduct since they are the ones presenting the offerings to God at the altar.  Making bald places on their heads, shaving the edges of their beard and cutting their flesh were all signs of morning when someone died, yet the priest were not to mourn in this way as many Israelites and other nations did.  We see the Lord tell Ezekiel not to mourn these ways when his wife dies.  Why do you think these rituals were done for the dead?  These were probably superstitious marks and trying to find someway to express the hurt of their heart.  We see this today in the common method of cutting to deal with depression among so many youth.  But cutting isn't a "new" thing but obviously practiced over many many centuries.  Now this isn't to say that the priests and Israelites can't mourn, but to not do it in disfiguring their body and for superstition or seeking comfort in a form not Godly.  They were to have hope in the resurrection and understanding of God's justice.  How do you mourn for the dead or deal with depression?