How do we know God's covenant includes both Jews and Gentiles?

The Apostle Paul makes it clear that God's covenant is not limited to the physical descendants of Abraham but extends to all who have faith. In Ephesians 2:13-19, Paul describes how those who were once far off, the Gentiles, are brought near by the blood of Christ and have become fellow citizens in God's household. This indicates that the promises and covenants made to the people of Israel extend to the Gentiles as well because they are all part of the spiritual Israel by faith. Romans 2:28-29 further emphasizes this distinction, stating that true circumcision is not of the flesh but of the heart, thus showing that God's covenant encompasses all who are regenerated, believing Jews and Gentiles alike.