As was typical in Paul’s letters, he began this one with a greeting, a thanksgiving, and a prayer. In these, he didn’t waste any words but gave some previews of the major themes of the letter.
In response to King Saul’s second major error and his excuse, Samuel famously declared that to obey is better than sacrifice.
In Stephen's speech before the Jewish Council, he gave a master class on the meaning of Old Testament history, which culminated in Jesus.
God is free to define Israel, to show mercy or wrath, and to add to Israel from the nations.