Paul clearly explains his message to the Galatians. He criticizes their unwise behavior and offers a better choice. That choice is freedom.
Christ has set us free: Christians are free to live by faith in Christ alone (see Romans 8).
do not be encumbered once more (literally do not take on a yoke): A yoke is a heavy wooden bar that joins two farm animals together, like oxen, so they can pull heavy loads. In the Jewish tradition, people used the word "yoke" to talk about following religious laws. It was a duty and honor to "take the yoke of the law." God's children in Jesus Christ are not meant to carry this heavy burden (see Luke 11:46; Acts 15:10). Instead, they follow the gentle guidance of Jesus, which brings freedom instead of heavy demands (Matthew 11:28–30).