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Galatians 3
1O foolish Galatians! Who has bewitched you? Before your very eyes Jesus Christ was clearly portrayed as crucified.
2I would like to learn just one thing from you: Did you receive the Spirit by works of the law, or by hearing with faith?
3Are you so foolish? After starting in the Spirit, are you now finishing in the flesh?
4Have you suffered so much for nothing, if it really was for nothing?
In other words, Paul already preached the Gospel to them, and they believed. We know they believed, because they received the Spirit. Christ only supplies His Spirit when we abide in Him--and we abide in Him by keeping His commands, which is the command to believe in the Name of God's Son and love one another. They were, afterward, told, however, "Yes, but you must serve by the Law of Moses, or else you're not accepted by God"--but the Law of Moses contains certain terms and conditions whereby it deals a curse on people who try to follow it, so they were coming under that curse and were not receiving the blessing of Abraham, which is the Spirit or the eternal life given to those who follow Christ.