The Lord hath sworn, and will not repent, Thou art a priest for ever after the order of Melchizedek. - Psalm 110:4
In the Old Testament times, the priests acted as mediators between God and man. Chosen and assigned by God, their duties were to pray for the people, offer sacrifices for the sin of the people and ultimately represent the people before holy God. It was an important job with strict regulations and was never to be taken lightly. The purpose of this arrangement was to act as a portrait of a time to come when God Himself would act as priest and mediator. Earthly sacrifices didn't pay for or cleanse anyone of sin. It was merely a covering in accordance with God's law--a picture of a higher and final sacrifice to come.
When Jesus died on the cross, He fulfilled the ultimate duty of a priest. As our go-between, He bridged the gap between our wickedness and God's holiness and made a way for us to enter into God's presence. Because of Jesus' great sacrifice, it is no longer necessary for us to use an earthly mediator to speak to God. We can go to God ourselves. We can go boldly into His presence because Christ paid for the right for us to do so. He is our High Priest, offering a one-time sacrifice unlike any other. With His precious blood, He paid for all the sins of the entire earth and set things right between God and man. But don't take my word for it. Look what the Bible has to say:
By so much was Jesus made a surety of a better testament. And they truly were many priests, because they were not suffered to continue by reason of death: But this man, because he continueth ever, hath an unchangeable priesthood. Wherefore he is able also to save them to the uttermost that come unto God by him, seeing he ever liveth to make intercession for them. For such an high priest became us, who is holy, harmless, undefiled, separate from sinners, and made higher than the heavens; Who needeth not daily, as those high priests, to offer up sacrifice, first for his own sins, and then for the people's: for this he did once, when he offered up himself. For the law maketh men high priests which have infirmity; but the word of the oath, which was since the law, maketh the Son, who is consecrated for evermore. 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. But now hath he obtained a more excellent ministry, by how much also he is the mediator of a better covenant, which was established upon better promises. - Hebrews 7:22-28 & Hebrews 8:1-6
A more excellent ministry. The mediator of a better covenant. Our High Priest. Yep, that's my God!