Peter prophesied on the Day of Pentecost that the Gospel with the promise of the Holy Ghost was not only for the Jews and their children, but also for the Gentiles – “to all that are afar off, even as many as the Lord our God shall call." (Acts 2:38-39).

In Peter’s epistle (letter) to the church, it appears he addresses those that were afar off - the Gentile Christians - but by the Gospel are now the people of God.

"But ye are a chosen generation, a royal priesthood, an holy nation, a peculiar people; that ye should shew forth the praises of him who hath called you out of darkness into his marvellous light:" - 1 Peter 2:9 KJV [“Peculiar” = “possession, one’s own property” (Thayer’s Greek Lexicon)]

The Gentile Christians are now fitting the description that was first used to describe the Jewish people in the book of Exodus. (Exodus 19:5-6).

Prophesies of the Gentiles coming out of darkness and into the light of Jesus are found in the Old Testament and fulfillment in the New Testament. (Isaiah 9:2, Matthew 4:12-16, Isaiah 42:6-7, Luke 1:76-79, Isaiah 60:3, Luke 2:25-32).

Then Peter went on to say,

"Which in time past were not a people, but are now the people of God: which had not obtained mercy, but now have obtained mercy." - 1 Peter 2:10 KJV

By the Gospel, and the fulfillment of Acts 2:39, Gentiles that believe and obey the Gospel are now the people of God. (Acts 14:27, Acts 15:3, 7-9, 14, Romans 9:22-33, Ephesians 2:1-22, Ephesians 3:1-21, Ephesians 4:4, 17-24, Ephesians 5:8, Romans 11:1-32).