What does the Bible say about true Israelites?

In John 1:47, Jesus declares that Nathanael is a true Israelite in whom there is no guile. This distinction goes beyond mere physical descent from Abraham. Paul elaborates in Romans 2:28-29, stating that a true Jew is one inwardly, and circumcision is that of the heart, in the spirit, not merely in the letter. This signifies that true Israelites are those who have experienced heart transformation and regeneration by God's grace, marked by sincere faith in God and obedience to His will.