The writers of the new testament quoted from the old testament often and expected the reader to understand the context and word meaning of the original quote. Romans 9:24-26 is just one example. If the source of those quotes is ignored, the context of the quote and the meaning intended is lost.
Romans 9:24-26 "Even us, whom he hath called, not of the Judeans only, but also of the Nations? As he saith also in Hosea, I will call them my people, which were not my people; and her beloved, which was not beloved. 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."
If one reads that without looking at Hosea then it allows one to teach that the “Not my people” could be anyone. Paul told us to look at Hosea because he wanted us to know who are those Not a People. The Not my People were Israelites of the Northern ten tribes whom God was divorcing and sending away to become known as Nations (incorrectly Gentiles). However God made a promise to those Not a People.
Hosea 1:10-11 "Yet the number of the children of Israel shall be as the sand of the sea, which cannot be measured nor numbered; and it shall come to pass, that in the place where it was said unto them, Ye are not my people, there it shall be said unto them, Ye are the sons of the living God. Then shall the children of Judah and the children of Israel be gathered together, and appoint themselves one head [Christ], and they shall come up out of the land: for great shall be the day of Jezreel."
The fulfillment of this prophecy is found in Ephesians chapter two.