Who was Paul warning in Galatians 5 and why?

Paul warned the Galatian believers against legalizers who were infiltrating congregations he had established in Asia Minor. He warned them not to return to the yoke of bondage—legalism, law, Judaism—or depend on fleshly works like circumcision for salvation, because adding anything to the cross makes Christ profit them nothing.

Les explains that the admonition is again directed to the Galatian believers, warning them not to fall victim to the legalizers who were making inroads into the congregations Paul had established in Asia Minor. Paul writes Galatians 5, telling them to stand fast in the liberty Christ has made them free and not be entangled again with the yoke of bondage—legalism, the law, Judaism. In verse 2, Paul says that if they be circumcised, speaking of salvation, and depend on something they can do in the flesh, Christ shall profit them nothing. Les notes this shook him up because millions of good people, even church members, depend on something of the flesh rather than relying totally on the finished work of the cross. He stresses that any one thing plus the cross cancels the work of the cross, so people must be warned.

Galatians 5:1

Stand fast therefore in the liberty wherewith Christ hath made us free, and be not entangled again with the yoke of bondage.

Who were the legalizers that Paul warned the Galatian believers about?

The legalizers were proponents of legalism, the law, Judaism, and circumcision who infiltrated congregations Paul established in Asia Minor. They urged flesh-based works as necessary for salvation. Paul warned the Galatian believers not to be entangled again in the yoke of bondage, since depending on anything in the flesh makes Christ profit nothing.