The Sumerians, Egyptians, and all ancient cultures had priests. Kings needed them for coronations, royal marriages, funerals, and for prayers as they went to war. They were those who knew how to offer animal sacrifice, and use the correct incantations. When the Aryans came into north India the Brahmins established themselves as a hereditary priesthood. In the sixth century BC there was a tidal wave of revolt against the corruptions of priestcraft (see for example Isaiah 1:11, Jeremiah 6:20). Within fifty years this wave of revolt moved from Iran to India and on to China, and back to ancient Greece. And it resulted in seven major religions which taught that priests were not needed (see Religion: Origins and Ideas chapter 3). These included Zoroastrianism, Buddhism, Jainism, Hindu Vedanta, Confucianism, Taoism, and the wave came back into the west with the atheistic philosophers of the Greek Golden Age.
But in each case a counter attack was mounted, and priests regained their power under new names. In North America we have an army of counselors and analysts who perform a similar function in every city. The problem is that they have to create faith in themselves rather in God the Creator.
In the Bible we are called a royal priesthood. That goes back to Abraham who seems to have functioned as both the leader of his people and their priest (see Genesis 12:7, 13:3-4, 18). After a battle to deliver his nephew Lot, he met with the priest king of Jerusalem. "King Melchizedek of Salem brought bread and wine (a precursor of our communion service); he was priest of God Most High." He blessed Abram, who recognized his royal priestly role by giving him a tithe of all the booty taken in battle (Genesis 14:18-20. The implications of this are set out in Hebrews 6:20-7:25).
Several centuries later when the children of Israel had come out of slavery in Egypt the LORD said to Moses "If you will obey my voice and keep my covenant, you shall be my treasured possession out of all the peoples. Indeed the whole earth is mine, but you shall be for me a priestly kingdom and a holy nation" (Exodus 19:5-6). That suggests that the whole nation was to be royal priesthood to serve all other nations. When Moses' brother Aaron was made the head of a line of hereditary priests that original vision was lost.
The term Royal Priesthood is used by Peter to explain his vision of the church which Jesus the Messiah was building. "You are a chosen race, a royal priesthood, a holy nation, God's own people, in order that you may proclaim the mighty acts of him who has called you out of darkness into his marvelous light" (1 Peter 2:9-10, obviously quoting Exodus 19:5-6).
What does our function as a royal priesthood in every city mean? We have ceremonial functions as we share in the praise of God and join in prayer for our nation, other nations, and those in need. In addition to that priests have a five-fold ministry to individuals. The hardest part is being able to listen patiently with great attention and without being judgmental. Having heard the worst, a priest then pronounces absolution, "You are forgiven." There should be a prayer to express to God that person's particular heart concerns. And we can teach something appropriate from the Scriptures. Finally the person must receive God's blessing, "All is well. God loves you."
Every Christian should be able and willing to perform those five priestly functions. And when we function in this way it is greatly appreciated. It costs nothing except the time needed to be with the person and listen. What people cannot bear is priests who load others with fussy religious duties, and engage in a ministry of condemnation.
The word royal means that as children of God we are viewed as part of the royal family under the sovereign LORD who "rules over the nations" (Psalm 22:28), "the King of glory" (Psalm 24:7-10, see 47:2-8). So when John the Baptist preached that "the kingdom of heaven has come near" (Matthew 3:2) he was announcing that the King of the Old Testament was now appearing among them. And Jesus himself taught about the principles of the Kingdom of Heaven (Matthew 3-10), and illustrated its working in parables (Matthew 13:18, 24, 43-47, 20:1, 22:2, 25:1).
This means that on the one hand we are planted in our city to serve as priests to listen, comfort, assure of forgiveness, teach and bless in the name of Jesus our gentle loving Shepherd. But we also serve as ambassadors of the Messiah King (2 Corinthians 5:20) and with all the authority of his Kingdom. In that capacity we announce his judgment and wrath and vindication among the nations (see Psalms 9:7-8, 9:12, 37:6).
As Mary sang "He has shown strength with his arm; he has scattered the proud in the thoughts of their hearts. He has brought down the powerful from their thrones, and lifted up the lowly; he has filled the hungry with good things, and sent the rich away empty" (Luke 1:51-53). The news that God is in control and cares for ordinary people, is great news for our city.