How do we know that God's promises have not failed?

In Romans 9:6, Paul asserts that 'the word of God has not failed' even though not all Israel is included in the promises. This is a crucial point because it demonstrates that being a part of God's covenant is not about physical lineage alone but about spiritual lineage through faith in the promised Messiah, Jesus Christ. In this way, God's faithfulness is displayed in His ability to fulfill His promises to those He has chosen—those who believe and trust in Him, regardless of their ethnic background. Thus, the assurance of God's promises can be found in the faithfulness of God and His election of believers both from the Jews and the Gentiles.