New Defender's Study Bible Notes
6:16 this rule. This phrase refers to the rule outlined in Galatians 6:14-15 of living as new creatures, glorying only in Christ and Him crucified (I Corinthians 2:2), and walking in the Spirit rather than the flesh.
6:16 Israel of God. The “Israel of God” is not a synonym for the church, but refers rather to those Jewish Christians in the church who were truly resting in the grace and liberty of Christ, justified by faith in His finished work of redemption—not in circumcision or any other works of the law. Paul was contrasting them with the Judaizers, the professing Jewish Christians who were troubling the Gentile Christians with their insistence on circumcision and Jewish ritualism in general, even while they themselves could not “keep the law” (Galatians 6:13) and indeed may well have been manifesting “the works of the flesh” rather than “the fruit of the Spirit” (Galatians 5:19-23). For other references to this true Israel versus rejected Israel, see Romans 4:12 and Romans 9:6-8.