17 I see him, but not now; I behold him, but not near—a star shall come out of Jacob,
and a scepter shall rise out of Israel; it shall crush the borderlands of Moab,
and the territory of all the Shethites. Numbers 24:17 (NRSV)
This would have been a strange prophecy for the Israelites to hear. This was a conformation of the prophecy in Gen 49:10 that the scepter would never depart from between Judah’s feet. All priests were to be of the tribe of Levi and Jacob was of the tribe of Judah. How could a priest rise out of the tribe of Judah? But God had a plan that would not violate the laws that He had handed down. When the scepter rose out of Israel, there would be a change in the way people were to worship God. This is explained further in Hebrews.
12 For when there is a change in the priesthood, there is necessarily a change in the law as well. 13 Now the one of whom these things are spoken belonged to another tribe, from which no one has ever served at the altar. 14 For it is evident that our Lord was descended from Judah, and in connection with that tribe Moses said nothing about priests. 15 It is even more obvious when another priest arises, resembling Melchizedek, 16 one who has become a priest, not through a legal requirement concerning physical descent, but through the power of an indestructible life.–Hebrews 7:12-15 (NRSV)
So, we see that while the priesthood of the Levites was established by the law, the priesthood of Jesus was established through the power of an indestructible life that could only be from the Creator. It was decided before the earth was formed. Jesus would be the final and perfect blood sacrifice for all the sin of the world. He was not, can not, and will not be destroyed or defeated. What Adam gave up in Eden, Jesus took back with His death and resurrection.
Now, we celebrate His birth, but that truly was just the beginning.