And from notes for v.9-10 in the New American Bible:
9. But you are "a chosen race, a royal priesthood, a holy nation, a people of his own, so that you may announce the praises" of him who called you out of darkness into his wonderful light.
10. Once you were "no people" but now you are God's people; you "had not received mercy" but now you have received mercy.
The prerogatives of ancient Israel mentioned here are now more fully and fittingly applied to the Christian people: "a chosen race" (cf
Isaiah 43:20-21) indicates their divine election (
Eph 1:4-6); "a royal priesthood" (cf
Exodus 19:6) to serve and worship God in Christ, thus continuing the priestly functions of his life, passion, and resurrection; "a holy nation" (
Exodus 19:6) reserved for God, a people he claims for his own (cf
Malachi 3:17) in virtue of their baptism into his death and resurrection. This transcends all natural and national divisions and unites the people into one community to glorify the one who led them from the darkness of paganism to the light of faith in Christ. From being "no people" deprived of all mercy, they have become the very people of God, the chosen recipients of his mercy (cf
Hosea 1:9;
2:23).