Priesthood has a long history stretching back to the Old Testament.
We are introduced to Israel’s priests shortly after their captivity in Egypt. From among the twelve tribes that composed the nation of Israel, God chose the priesthood from the tribe of Levi. Priesthood was therefore based entirely on ancestry.
Their duty consisted in representing the people before God and offering sacrifices on their behalf. However, it was not God’s intention that this type of priesthood should last forever. Jesus introduced a priesthood that embraces all Christians. It would not be composed of men born into the tribe of Levi, but would embrace all men and women who have been ‘born again of water and the Holy Spirit.’ (John 3:5)
One does not need to have a vocation to be a priest. Neither does one require years of special training. Scripture make it very plain that if you are a Christian you are a priest and part of the ‘royal priesthood’. (1 Peter 2:9) Furthermore, your body is the temple of the Holy Spirit. (1 Corinthians 6:19-20) And, as a priest, you can offer to God ‘spiritual sacrifices’. (Hebrews 13:15-16)
Where there is a Christian, there is also a priest. There is also a temple and spiritual sacrifices can be offered to God. This is the ‘royal priesthood’ revealed in the Word of God.