The question, What is the sanctuary? is clearly answered in the Scriptures. The term “sanctuary,” as used in the Bible, refers, first, to the tabernacle built by Moses, as a pattern of heavenly things; and, secondly, to the “true tabernacle” in heaven, to which the earthly sanctuary pointed. At the death of Christ the typical service ended. The “true tabernacle” in heaven is the sanctuary of the new covenant.
The holy places of the sanctuary in heaven are represented by the two apartments in the sanctuary on earth. As in vision the apostle John was granted a view of the temple of God in heaven, he beheld there “seven lamps of fire burning before the throne.” Revelation 4:5. He saw an angel “having a golden censer; and there was given unto him much incense, that he should offer it with the prayers of all saints upon the golden altar which was before the throne.” Revelation 8:3. Here the prophet was permitted to behold the first apartment of the sanctuary in heaven; and he saw there the “seven lamps of fire” and the “golden altar,” represented by the golden candlestick and the altar of incense in the sanctuary on earth. Again, “the temple of God was opened” (Revelation 11:19), and he looked within the inner veil, upon the holy of holies. Here he beheld “the ark of his testament,” represented by the sacred chest constructed by Moses to contain the law of God....
Moses made the earthly sanctuary after a pattern which was shown him. Paul teaches that that pattern was the true sanctuary which is in heaven. And John testifies that he saw it in heaven.
The sanctuary in heaven is the very center of Christ’s work in behalf of men. It concerns every soul living upon the earth.
When Christ ascended to heaven, He ascended as our Advocate. We always have a Friend at court. FLB 202
If you would have a clean record in the books of heaven, never fret or scold. Let your daily prayer be, “Lord, teach me to do my best. Teach me how to do better work. Give me energy and cheerfulness.” Pr 161
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. Hebrews 8:1-2 (King James Version)