As he says also in Hosea,
I will call them my people, who were not my people; and her beloved, who was not beloved.
All Commentaries on Romans 9:25 Go To Romans 9
Ambrosiaster
AD 400
It is clear that this was said about the Gentiles, who once were not God’s people, but afterward, to the chagrin of the Jews, received mercy and are called God’s people. Once they were not loved, but when the Jews fell away they were adopted as children and are now loved, so that where once they were not called God’s people, now they are called children of the living God. Commentary on Paul’s Epistles.