Peter adds a purpose clause to explain God’s intent. They are a chosen race, a royal priesthood, a holy nation, God’s treasured possession in order that they may proclaim God’s excellencies in the world around them. Their identity is not meant to be a secret kept to oneself but instead is evidence to “those who do not believe” (1 Peter 1:7) that God has in fact involved himself in this world.
9 But you are a chosen race, a royal priesthood, a holy nation, a people for his own possession, that you may proclaim the excellencies of him who called you out of darkness into his marvelous light.