A.T. Robertson Commentary 1 Peter 2:9

"But ye are a elect race, a royal priesthood, a holy nation, a people for [God`s] own possession, that ye may show forth the excellencies of him who called you out of darkness into his marvellous light:" — 1 Peter 2:9 (ASV)

But ye (υμεις δε). In contrast with the disobedient ones.

An elect race (γενος εκλεκτον). From Isa 43:20. The blood relation of the spiritual Israel (not the Jewish race) through the new birth (1:23).

A royal priesthood (βασιλειον ιερατευμα). From Ex 19:6 (cf. Revelation 1:6; 5:10). The official in Christian churches is πρεσβυτεροσ=επισχοπος, not ιερευς. We are all ιερεις (priests). Cf. 2:5.

A holy nation (εθνος αγιον). Also from Ex 19:6, but here applied, not to the national Israel, but to the spiritual Israel of believers (both Jews and Gentiles).

A people for God's own possession (λαος εις περιποιησιν). The idea here occurs in Ex 19:5; Deuteronomy 7:6; 14:2; 26:18, where we have λαος περιουσιος as in Tit 2:14 (alone in the N.T.), and in Mal 3:17 we find εις περιποιησιν (for a possession). Περιουσιος λαος is a people over and above the others and περιποιησις is a possession in a special sense (Ephesians 1:14). See Paul's use of περιεποιησατο in Ac 20:28. The old rendering, "a peculiar people," had this idea of possession, for "peculiar" is from pecus (Latin for flock).

That ye may shew forth (οπως εξαγγειλητε). Purpose clause with οπως, rather than ινα, with the first aorist active subjunctive of εξαγγελλω, old verb, to tell out, here alone in N.T.

The excellencies (τας αρετας). From Isa 43:21. Old word for any preeminence (moral, intellectual, military), often for "virtue," but not in that sense in the O.T. or the N.T. The word has the sense of moral worth in 2 Peter 1:3,5; Php 4:8; and the Apocrypha. In Isaiah (here quoted) it means praise and glory to God. So also Isa 42:12. See Ac 2:11 τα μεγαλεια του θεου (the mighty works of God).

Darkness (σκοτους). Heathenism.

His marvellous light (το θαυμαστον αυτου φως). Christianity. For θαυμαστον (from θαυμαζω) see Mt 21:42. For the change from heathenism to Christianity see Col 1:12; Ephesians 5:8–14.