“I do not frustrate the grace of God: for if righteousness come by the law, then Christ is dead in vain” (Galatians 2:21).
You’ve probably heard people say, “Don’t make the grace of God vain”. It’s a good statement if they know what they are saying. Paul is very clear about how the grace of God may not be appropriated: “And if by grace, then is it no more of works: otherwise grace is no more grace. But if it be of works, then is it no more grace: otherwise work is no more work” (Romans 11:6). Graces ceases to be grace if work is involved.
For instance, the employer giving me a salary at the end of the month is not an act of grace. I worked for it. Grace ceases to be grace when work is involved. Grace is also wasted when work is involved. If you didn’t know I had paid a driver to drop you at a certain destination, and you walked the distance, my provision was in vain. This is exactly how the grace of God can be made vain: when you to think that you still need to work to earn his favour.
This is what Paul means when he says: “I do not frustrate the grace of God: for if righteousness come by the law, then Christ is dead in vain”. Galatians 2:21. To not accept righteousness as what it is- a free gift- is to frustrate the grace of God.