Hebrews 8:1-5
Heb 8:1 (KJB)
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;
Sum - Main point or principal thing
The writer now gives a summation of the main point of what he has been previously teaching. The Lord Jesus Christ has completely fulfilled all the requirements of God’s holy law and as such has sat down on the right hand of God. Sitting down refers to the completion of something. Jesus is not like the high priest from among men but is eternal as he now sits at the right hand of God the Father in the heavens. The earthly priests had to stand continually when performing their service on a repetitive basis but the Lord Jesus now sits which means the service of His sacrifice has been completed once and for all, so now He rests being seated at the right hand of God.
Heb 8:2 (KJB)
A minister of the sanctuary, and of the true tabernacle, which the Lord pitched, and not man.
Minister - One who serves in an office or ministry
Of the sanctuary - The holies or the holy things
Pitched - Set up or set in place
Christ’s priestly service does not occur in the tabernacle of earth which was made by man but His place of service is in Heaven, which is the true tabernacle. The tabernacle which was on earth was only a shadow of the true one in Heaven. The term tabernacle in the New Testament is also used for one’s body. (2 Pet 1:14 KJV) Knowing that shortly I must put off this my tabernacle, even as our Lord Jesus Christ hath showed me. The true tabernacle which the Lord pitched was also the body of believers for whom He is the High Priest. The words “of the sanctuary” is also translated as “holies” and because of Christ’s sacrifice on Calvary the believer is made holy.
Heb 8:3 (KJB)
For every high priest is ordained to offer gifts and sacrifices: wherefore it is of necessity that this man have somewhat also to offer.
Necessity - Necessary
All the High Priests which were appointed by God for the service of the earthly tabernacle had responsibilities and tasks to perform. On behalf of the people they had offered gifts and sacrifices such as sin offerings as in the yearly Day of Atonement. The offerings and sacrifices they made to God was a necessary part of this Priestly office. When the Lord Jesus Christ came on the scene as the High Priest, it was also necessary that He have something to offer. Instead of offering the bulls and goats for sacrifices, He, by Himself, had made complete atonement for the body of Christ. The sacrifice He offered was Himself and it was sufficient to remove the sins from all those He came to save.
Heb 8:4 (KJB)
For if he were on earth, he should not be a priest, seeing that there are priests that offer gifts according to the law:
If Jesus was on earth, He would be totally disqualified from being a priest because He was not of the tribe of Levi and not in the lineage of Aaron. Those who were from those lineages were qualified to be an earthly priest according to the law of God. (Num 1:49-50 KJV) Only thou shalt not number the tribe of Levi, neither take the sum of them among the children of Israel: {50} But thou shalt appoint the Levites over the tabernacle of testimony, and over all the vessels thereof, and over all things that belong to it: they shall bear the tabernacle, and all the vessels thereof; and they shall minister unto it, and shall encamp round about the tabernacle. This verse may also give an insight into the date Hebrews was written. The word “offer” is in the present tense which means that the sacrifices may have still been going on at the time of the writing of Hebrews. This would mean that Hebrews was written before 70 A.D.
Heb 8:5 (KJB)
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 showed to thee in the mount.
(Exo 25:40 KJV) And look that thou make them after their pattern, which was showed thee in the mount. Here the writer was stating that the earthly priests who served in the tabernacle and the temple were only doing it as a shadow of the heavenly reality. Sometimes it may seem that the shadow in religion holds a great appeal to the flesh. When they saw the animal sacrifices and the priests in their ritualistic garb it gave them a sense of security but the reality of it was that these things were nothing but a shadow and since the cross of Christ when the veil was rent in two, the animal sacrifices held no more meaning since the shadow was now replaced by the anti-type, Christ Himself. Since Israel refused to halt the animal sacrifices after the crucifixion, God sent General Titus to Jerusalem in 70 A.D to stop it for them. God was no longer accepting the Mosaic sacrifices since His Son had made the final sacrifice, which was what all the animal sacrifices were looking forward to. The writer was warning the Hebrews not to turn back to Judaism and the animal sacrifices since they would be turning from the heavenly reality which is Christ, to the earthly shadow which is the law.