We believe that the center of divine service in Old Testament times was the sanctuary, first in the form of a portable tent, and later built as a temple. The earthly sanctuary consisted of the courtyard, the Holy Place, and the Most Holy Place. The sacrifices were offered in the courtyard. Hebrews 9:1-7. By means of the blood, sin was transferred to the sanctuary, and it thereby became defiled. The sacrifices brought because of sin pointed to Jesus, the “Lamb of God, which taketh away the sin of the world.” John 1:29. The priests were chosen as mediators between God and man.

Once a year, on the great Day of Atonement, the sanctuary was cleansed. The high priest went into the Most Holy Place and sprinkled the blood from the sin offering on and before the ark of the covenant. The requirements of the law were thus fulfilled. Then, as mediator, he took the sins upon himself and carried them out of the sanctuary. They were transferred to a living goat, which was then led away into the desert. Through these ceremonial acts, the people were reconciled; and the sanctuary, cleansed. 
Romans 6:23 – 
For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.
Leviticus 16:15, 16, 20-22 – 
Then shall he kill the goat of the sin offering, that is for the people, and bring his blood within the vail, and do with that blood as he did with the blood of the bullock, and sprinkle it upon the mercy seat, and before the mercy seat: And he shall make an atonement for the holy place, because of the uncleanness of the children of Israel, and because of their transgressions in all their sins: and so shall he do for the tabernacle of the congregation, that remaineth among them in the midst of their uncleanness. And when he hath made an end of reconciling the holy place, and the tabernacle of the congregation, and the altar, he shall bring the live goat: And Aaron shall lay both his hands upon the head of the live goat, and confess over him all the iniquities of the children of Israel, and all their transgressions in all their sins, putting them upon the head of the goat, and shall send him away by the hand of a fit man into the wilderness: And the goat shall bear upon him all their iniquities unto a land not inhabited: and he shall let go the goat in the wilderness.

This sanctuary on earth had its original pattern in heaven, where Jesus is the High Priest today. Only through His mediatorial work can the believer obtain forgiveness, justification, and sanctification.
1 Timothy 2:5, 6 – For there is one God, and one mediator between God and men, the man Christ Jesus; Who gave himself a ransom for all, to be testified in due time. 
Hebrews 8:1-5 – 
Now of the things which we have spoken this is the sum: We have such an high priest, who is set on the right hand of the throne of the Majesty in the heavens; A minister of the sanctuary, and of the true tabernacle, which the Lord pitched, and not man. For every high priest is ordained to offer gifts and sacrifices: wherefore it is of necessity that this man have somewhat also to offer. For if he were on earth, he should not be a priest, seeing that there are priests that offer gifts according to the law: Who serve unto the example and shadow of heavenly things, as Moses was admonished of God when he was about to make the tabernacle: for, See, saith he, that thou make all things according to the pattern shewed to thee in the mount. 

Hebrews 9:11, 12, 15 – But Christ being come an high priest of good things to come, by a greater and more perfect tabernacle, not made with hands, that is to say, not of this building; Neither by the blood of goats and calves, but by his own blood he entered in once into the holy place, having obtained eternal redemption for us… And for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance. 
Revelation 11:19 – 
And the temple of God was opened in heaven, and there was seen in his temple the ark of his testament: and there were lightnings, and voices, and thunderings, and an earthquake, and great hail.

“The sanctuary in heaven is the very center of Christ’s work in behalf of men. It concerns every soul living upon the earth. It opens to view the plan of redemption, bringing us down to the very close of time and revealing the triumphant issue of the contest between righteousness and sin.”

“The intercession of Christ in man’s behalf in the sanctuary above is as essential to the plan of salvation as was His death upon the cross. By His death He began that work which after His resurrection He ascended to complete in heaven. We must by faith enter within the veil, ‘whither the forerunner is for us entered.’ Hebrews 6:20.” – The Great Controversy, pp. 488, 489.