'You shall not make any cuts in your body for the dead nor make any tattoo marks on yourselves: I am the LORD. (Leviticus 19:28)
The literal commandment is that we should not make any cuts on our bodies for the dead.
Messiah implicitly affirmed this commandment when He spoke about the Law:
"Do not think that I came to abolish the Law or the Prophets; I did not come to abolish but to fulfill. For truly I say to you, until heaven and earth pass away, not the smallest letter or stroke shall pass from the Law until all is accomplished. Whoever then annuls one of the least of these commandments, and teaches others to do the same, shall be called least in the kingdom of heaven; but whoever keeps and teaches them, he shall be called great in the kingdom of heaven. (Matthew 5:17-19)
He also offered words of comfort to those who grieve:
Blessed are those who mourn, for they shall be comforted. (Matthew 5:4)
This commandment indicates that we should not depart from the way G-d has ordered His creation... even when we suffer great grief and great loss as when we mourn those who have died. Each of our bodies is formed the way G-d intended for it to be. This commandment pictures Messiah's complete obedience to G-d's order for creation.
Even in His grief at the death of Lazarus, He sought the Father's will:
Jesus wept.Then Jesus raised His eyes, and said, "Father, I thank You that You have heard Me. I knew that You always hear Me; but because of the people standing around I said it, so that they may believe that You sent Me." (John 11:35, 41-42)
Messiah knew His role in Creation and stood firm in that role even as He wept and mourned the loss of His friend and shared in the grief of others.
Messiah fulfilled this commandment by not tearing or cutting His skin in mourning.
This commandment is observed in a very literal fashion: tearing or cutting the skin in mourning is forbidden. Such behavior is generally associated with pagan practices and idolatry and was forbidden to G-d's people.
We are able to fulfill this commandment today and we should not tear or cut our skin in mourning.
Grief can be expressed in myriads of ways. The gracious G-d of the universe set boundaries for us that, even when we are afflicted with grief of any kind, protect us from ourselves.
In his letter to the Thessalonicans, Paul says that he does not want us to grieve like people who have no hope. (1 Thessalonians 4:13-14) When we obey this commandment, we are grieving like those who do have hope in our Creator and Redeemer.