In this world, there is what is called the “separation of church and state” or “separation of church and government”.
However, in the New Heavens and New Earth there will be no separation of “church and government” because before Jesus was born the prophet Isaiah said: “Of the increase of his government and peace there shall be no end, upon the throne of David, and upon his kingdom, to order it, and to establish it with judgment and with justice from henceforth even forever. The zeal of the LORD of hosts will perform this” (Isaiah 9:6–7).
JESUS is the High Priest in addition to the “only Potentate, the King of kings, and Lord of lords…” (1 Timothy 6:15, 1:17). “The LORD hath sworn, and will not repent, Thou art a priest for ever after the order of Melchizedek” (Psalm 110:4).
“But Christ as a son over his own house; whose house are we, if we hold fast the confidence and the rejoicing of the hope firm unto the end” (Hebrews 3:6).
“And having an high priest over the house of God; Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water. Let us hold fast the profession of our faith without wavering; (for he is faithful that promised;) And let us consider one another to provoke unto love and to good works” (Hebrews 10:21-24).
Furthermore, in the Book of Revelation, John clearly expressed that they will be kings and priests in the Kingdom of God, the Father saying:
“JOHN to the seven churches which are in Asia: Grace be unto you, and peace, from him which is, and which was, and which is to come; and from the seven Spirits which are before his throne;
And from Jesus Christ, who is the faithful witness, and the first begotten of the dead, and the prince of the kings of the earth. Unto him that loved us, and washed us from our sins in his own blood,
And hath made us [KINGS AND PRIESTS] unto God and his Father; to him be glory and dominion for ever and ever. Amen” (Revelation 1:4-6).