The purpose of the sanctuary was to illustrate God's way, through Christ, of saving mankind. Remember, we're told that God's way "is in the sanctuary" Psalm 77:13. It is there that He separates sin from sinners so that sin can be destroyed while repentant sinners are saved, but one will not be sorry or repentant for sin unless they have some concept of what sin costs. How can that be conveyed? Put yourself back in time.
You have broken the law and are deserving of death, but being truly sorry for that sin, you follow God's instructions for getting rid of it. Leading a frolicking healthy lamb, you are on your way to the sanctuary, which is in the middle of the encampment.
The sanctuary is made up of an outer court and the tabernacle which is divided into two compartments, the Holy Place and the Most Holy Place. As you approach the entrance to the sanctuary, you are directed just inside the court to the side of the altar of sacrifice (also called the altar of burnt offering). Can you hear the bleating of that little lamb you're leading? Now you lay your hand on the innocent animal and confess your specific sin which, by faith, is transferred from you to the substitute. You are allowing that innocent one, prefiguring Christ, to take the penalty for your sin. "The LORD hath laid on him the iniquity of us all" Isaiah 53:6.
The substitute must die. "Without shedding of blood is no remission" Hebrews 9:22. Who will slay the lamb? You, the sinner, must slay the sacrifice. Other types of sacrifices were slain by the priests, but where individual sin was concerned, the sinner must do so. It is your sin that made this death necessary. "The wages of sin is death" Romans 6:23. The knife is in your hand, but with what difficulty you use it to take life! Can you picture looking into the eyes of that innocent lamb as it is dying because of your sin? Let this thought sink deeply into your heart.
Jesus is "the Lamb of God, which taketh away the sin of the world" John 1:29. He is the One we have slain by our transgression of God's law of love. "He was wounded for our transgressions, he was bruised for our iniquities: the chastisement of our peace was upon him; and with his stripes we are healed" Isaiah 53:5.
As you leave the sanctuary to return home, you would understandably be filled with solemn thoughts regarding the awful costliness of sin as well as a profound gratitude for God's grace in providing a substitute.