Galatia was a Roman province in Asia Minor. It was the name
for what is today central Turkey. The Apostle Paul established
a number of "ecclesias" (assemblies of Christians)
there during his missionary journeys.
Paul wrote this letter to answer false teachings that were
being introduced in the Galatian churches. Some of the Jewish
Christians were trying to persuade believers that they ought
to keep the Law of Moses.
Paul reminds his readers that he was once a zealous supporter
of the Law of Moses and of Judaism. But Jesus had personally
appeared to him (Acts 9) and this had convinced him to become
a Christian. His account of this is in chapter 1 of this letter.
In this letter, Paul reminds his readers that trying to keep
the Law of Moses does not make a man "righteous"
(good). God counted Abraham as righteous when he believed
God. Paul shows, in chapter 3, that people who have faith
in God's promises are pleasing to Him.
The Law was given by God, so it must have had a purpose.
Galatians 3:19 shows it was intended to make people realise
they were sinners needing forgiveness. The Law was only to
last until Christ came, as the real sacrifice for sinners
(3:24). Christ had now certainly come!
The Law, says Paul, was only a "custodian" (guardian)
- like someone to take care of children until they're grown
up. Now Christians were like grown up "sons of God"
(3:25). Those who believe the promises and are baptised into
Christ change their way of life. They have "put on"
Christ and are thus covered by his righteousness. Paul may
well have had in mind the practice of the time when a young
man would have "put on" a toga - an outer garment
warn by adult Romans - to mark the change to manhood.