When is that opportunity? Paul’s point is that the believer’s entire life provides the unique privilege by which one may serve others in Christ’s name. In addition, our love for fellow Christians is the primary test of our love for God.
Commentary from the MacArthur study Bible, notes for Galatians 6:10.
The freedom Christians have is not a base from which they can sin freely and without consequence. Christian freedom is not for selfish fulfillment, but for serving others.
This does not mean God has abrogated His moral law (Romans 3:21). We are indeed under grace (Romans 6:14), but the Lord also guides and teaches us in the behavior He expects, by giving us His words and Spirit as that guide.
Commentary from the MacArthur study Bible, notes for Galatians 5:13, Romans 6:14.
God or gods, to which do you commit?