But Christ became a priest with God’s oath. God said to him, “The Lord has made a promise with an oath and will not change his mind: ‘You are a priest forever.’” Psalm 110:4
The law chooses high priests who are men and have the same weaknesses that all people have. But after the law, God spoke the oath that made his Son high priest. And that Son, made perfect through suffering, will serve forever.
The people were given the law under the system of priests from the tribe of Levi. But no one could be made spiritually perfect through that system of priests. So there was a need for another priest to come. I mean a priest like Melchizedek, not Aaron.
God is not a man; he will not lie. God is not a human being; his decisions will not change. If he says he will do something, then he will do it. If he makes a promise, then he will do what he promised.
He will build the Lord’s Temple, and he will receive the honor. He will sit on his throne and be the ruler, and a priest will stand by his throne. These two men will work together in peace.’