Hebrews Chapter 7 speaks of Melchizedek and his greatness.
Now consider how great this man was, to whom even the patriarch Abraham gave a tenth of the spoils. Hebrews 7:4 NKJV
However, Chapter 7 also refers to a new priest that has come who belongs to another tribe, from which no man as officiated at the altar. Plus, if there was a change a priesthood, there was also a change of the law. That man was Jesus, who came from Judah. Jesus did not become a priest because a man appointed Him either. Jesus’ life is eternal. Man is held back by death and sin. Therefore, priests had to offer up sacrifices for their own sins and then for the people. Multiple priests had been established because they would die and a new one would be appointed.
We are so fortunate to live under Jesus Christ as our High Priest. He is without sin and does not need to offer up sacrifices. He made the ultimate sacrifice by becoming the perfect sacrifice Himself. Jesus can save all who come to God through Him. He does not die and can always make intercession for us. The law made nothing perfect. Jesus is the one who brought a better hope through which we can draw near to God.
For on the one hand there is an annulling of the former commandment because of its weakness and unprofitableness, for the law made nothing perfect; on the other hand, there is the bringing in of a better hope, through which we draw near to God. Hebrews 7:18-19 NKJV
But He, because He continues forever, has an unchangeable priesthood. Therefore He is also able to save to the uttermost those who come to God through Him, since He always lives to make intercession for them. For such a High Priest was fitting for us, who is holy, harmless, undefiled, separate from sinners, and has become higher than the heavens; who does not need daily, as those high priests, to offer up sacrifices, first for His own sins and then for the people’s, for this He did once for all when He offered up Himself. For the law appoints as high priests men who have weakness, but the word of the oath, which came after the law, appoints the Son who has been perfected forever. Hebrews 7:24-28 NKJV