As the good news about Jesus began to be preached and welcomed among people who were not Jews, the question arose as to whether a person must obey the Law of Moses in order to be a true Christian.
This letter was written around 49 AD in order to bring back to true faith and practice those people who were being misled by this false teaching.
Faith is the only way to be saved. Paul insists that this was true already for Abraham, who had received God's promise by faith. And Paul leaves a proclamation about what his own faith means to him as well as to anyone who follows Christ.
"I have been nailed to the cross with Christ. I have died, but Christ lives in me. And I now live by faith in the Son of God, who loved me and gave his life for me." (2:20)