The church of the New Testament prophesied
From Romans 9:25,26 and 1 Peter 2:10 we may notice how Hosea 1:10 has been fulfilled in Christ and His New Testament people.
Peter's first epistle is replete with direct quotes and allusions to the Old Testament, weaving a rich tapestry of revealed truth by showing how the prophets of old spoke of the last days which the Christ, by his incarnation, has inaugurated.
In fact, all others writers of the New Testament may be said to be giving their commentary on the Old Testament and explaining how it is fulfilled in Christ. "Not a people but now the people of God." The Greek word laos is used in the Septuagint primarily for Israel. There is in Peter a continuity of application to the New Testament ecclesia prophetical texts at face value dealing with Israel. Peter draws on Hosea 1:6,9,10.
In its original context this is a prophecy about God's embracing Israel after He had rejected her: a restoration after judgement. Peter interprets the Hosea passages to include the reception of Gentiles into the people of God, as James also quotes Amos during the Jerusalem council to prove that God was indeed welcoming Gentiles unto salvation, referring to the "tabernacle of David" to being rebuilt through Gentiles receiving the gospel.
All this shows that in the mind of the apostles God's mercy extends to undeserving Jew and Gentiles alike, and there is essential continuity between Old Testament Israel and the New Testament church, to such an extent that Paul calls all New Testament believers, "the Israel of God" (Galatians 6:16).
At first glance in reading Hosea it might be concluded that God's interest is with national Israel only. But not so. As spokesmen for the Lord Jesus, the apostles give it a wider interpretation. Paul does this after affirming that God's election extends also to Gentiles: "even us whom He called, not of the Jews only, but also of the Gentiles" (Romans 9:24). And as proof positive he quotes Hosea immediately afterward.
So we must be careful to maintain that what the prophets spoke of is being fulfilled in the church today. This we must do in opposition to the Dispensationalist error of picturing the church as an "intercalary" dispensation, before the inauguration of the Millennial kingdom.