25 As he saith also in Osee, I will call them my people, which were not my people; and her beloved, which was not beloved. 26 And it shall come to pass, that in the place where it was said unto them, Ye are not my people; there shall they be called the children of the living God. (Romans 9:25-26 KJV)
William Burkitt’s Commentary
Apostle Paul having hitherto vindicated the wisdom and righteousness of God in the rejection of the Jews, and calling of the Gentiles; lest the Jews should stumble and take offence at it, in these and the following verses, he proves that the calling of the Gentiles was long before foretold, both by the prophet Hosea and the prophet Isaiah; by the prophet Hosea,
I will call them my people, which were not my people. Ho 2:23
And, Instead of, ye are not my people, it shall be said, ye are the sons of the living God. Ho 1:10
Which expressions signify and import God’s receiving the Gentiles into the church as an act of free and undeserved mercy, whom the Jews looked upon as castaways, as strangers, as dogs; accounting themselves only to be of his family and household. Next, he produces the testimony of Isaiah.