Paul uses the scriptures in Hosea 1:9-10 to include the Gentiles as well. What Paul is showing is that the Gentiles generally were not called “God’s People”, simply because of their rejection of Him, and the fact a covenant was made with Abraham (Who was not a Jew when God dealt with him). The idea is that it was always in God’s plan to“Receive as His people those who were formerly not His people”. As stated before, it was always in the Will of God to include every human being in His Salvation Plan. See John 3:16