The Old Testament is the narrative of how God chose a group of people to be a special showcase to the world of His power and love.  Although He had chosen them, very many turned away from Him, alienating themselves from their privileged position.  On the other hand, God also loved the Gentiles who had not been 'chosen' under the old covenant.  Although the Jews considered them to be aliens, God wanted to bring them into His family (John 10:16).

It did not seem fair.  Some Jesus-following Jews in the church in Rome did not fully understand how Gentiles could be included in God's family.  Previously these non-Jewish people, with all kinds of pagan religious backgrounds, had no love for the one true God, and did not have any interest in obeying His law.  Yet, although they had not pursued righteousness, God had pursued them.  And all those who believed in Jesus were made righteous because of His sacrifice on their behalf (Romans 5:19).

Every pious Jew tried to be 'in the right' with God by keeping the rules (as written in the first five books of the Old Testament).  But that was unsatisfactory for two reasons: firstly, they could never keep on doing everything right; and even when they did, the legacy of their sins weighed them down so that God still felt remote.  Yet God has implanted a deep desire into all human beings to find Him (Job 23:3).

Although it might seem shocking to us, some of the Jewish Christians in Rome did not think that the Gentile Christians were 'proper believers in God', because they had not become Jews.  Paul emphasised that it did not matter what religious background people come from (Romans 3:22); all that matters is that people come to God through believing in Jesus as Saviour and Lord.