Speaking to the Israelites God declared: "You will be for me a kingdom of priests and a holy nation." (Exod 19:6). God's design was for the whole nation was to act as heralds and mediators of his grace to the peoples of the earth.
This was repeated to the church in the New Testament: "But you are a chosen people, a royal priesthood, a holy nation, a people belonging to God, that you may declare the praises of him who called you out of darkness into his wonderful light." (1 Pet 2:9)