Although Christ is the root of Jesse (David's father, signifying the Jewish people), He will also be the ruler of the Gentiles. The apostle quoted this word and the word in vv. 9-11 to prove that Christ brings together the Gentiles and the Jews. Since Christ is such an all-embracing Lord (Acts 10:36), bringing together the Jews and the Gentiles, we must receive all the different believers according to Him.
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