Who was Jesus Christ a minister to?

Jesus Christ was a minister to the circumcision, which refers to the Jews. He ministered for the truth of God in order to confirm the promises made unto the fathers—Abraham, Isaac, and Jacob. This teaching is drawn from the provided context.

Les explains that Jesus Christ was a minister of the circumcision, and he clarifies that the people of the circumcision are the Jews. He says you can substitute 'Jews' for 'circumcision' without violating Scripture. The purpose was to confirm the promises made unto the fathers, Abraham, Isaac, and Jacob. Les connects this to the Abrahamic Covenant in Genesis chapter 12, noting that all these things are seeded in the Old Testament, even though the doctrine of Christ's death, burial, and resurrection is not found there. The Old Testament provides the foundation, going all the way back to Genesis 3.

Romans 15:8

Now I say that Jesus Christ was a minister of the circumcision for the truth of God, to confirm the promises made unto the fathers:

Why was Jesus Christ a minister of the circumcision?

Christ served as a minister of the circumcision—that is, the Jews—for the truth of God. His purpose was to confirm the promises made to the fathers: Abraham, Isaac, and Jacob. This ministry to Israel demonstrated God's faithfulness and pointed back to the Abrahamic Covenant.