Note 1 at Gal. 4:21: Those who advocate obtaining righteousness by keeping the law don't know what they are saying (1 Tim. 1:7). You can't just keep part of the law. You have to keep every precept of the law perfectly or you've broken the whole thing (see note 15 at Gal. 3:10, p. 1066). Paul now uses the Old Testament scriptures which the legalistic Jews had perverted to prove the gospel he had preached.