Galatians 2:21: I do not frustrate the grace of God: for if righteousness come by the law, then Christ is dead in vain.
The word “vain” appears in the New Testament 38 times. In the context above, vain means “useless” or “ineffectual.”
There are three crucial points to Galatians 2:21.
First, Paul doesn’t participate in frustrating grace, and neither should we. Nor should we have anything to do with those who frustrate grace.
2 John 1:10-11:
 If there come any unto you, and bring not this doctrine, receive him not into your house, neither bid him God speed:
 For he that biddeth him God speed is partaker of his evil deeds.
Second, to try to be justified by the law is to frustrate grace. Like the word “vain”, the word “frustrate”, in this case, also means to make ineffectual.
Third, there is no law that could provide righteousness to mankind. If there were, then Christ need not have died to pay for our sins.
Galatians 3:21: Is the law against the promises of God? God forbid: for if there had been a law given which could have given life, verily righteousness should have been by the law.
As believers in Christ, we know that Jesus has saved us completely. We know that He paid the FULL price for our sins. We know that we didn’t contribute to our salvation by forsaking our sins, confessing our sins, saying a prayer, walking an aisle, committing to reform ourselves, or by allowing Jesus to change our lives. We know that when we believed in Jesus, we received eternal life that can never be lost or forfeited.
We know that our righteousness comes from Christ, and not our attempts to keep the law, whether it be God’s perfect law or the Lordship “salvationists'” (LSers) arbitrary laws. In other words, we know that Christ is not dead in vain. We know that He is risen and alive and that we have eternal life through Him.
 But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets;
 Even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe: for there is no difference:
 For all have sinned, and come short of the glory of God;
 Being justified freely by his grace through the redemption that is in Christ Jesus:
 Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God;
 To declare, I say, at this time his righteousness: that he might be just, and the justifier of him which believeth in Jesus.
LSers frustrate grace by insisting that simply believing in Jesus is not sufficient to either receive, keep, or evidence eternal life. In so doing, they create a false gospel of works, devoid of power to save those who trust in that false gospel for eternal life. And, for those Christians who are duped into LS after they receive eternal life, they are robbed of any power for Christian living or evangelizing the lost.
In Romans 4, the Apostle Paul confirms that the admixture of faith in Christ PLUS works for eternal life is not possible :
Romans 4:14: For if they which are of the law be heirs, faith is made void, and the promise made of none effect.
Notice the similarity between Galatains 2:21 and Romans 4:14. If we could be justified by the law, Christ is dead in vain. If those trying to be justified by the law could be justified by the law, then justification by faith is of no effect.
If you ask an LSer what “believe in vain” means, you will likely get some answer that has to do with one’s works. For example, that someone may believe in Jesus, but not have eternal life, because they haven’t turned from their sins, or they haven’t shown sufficient good works. They may throw “faith without works is dead” or “even the demons believe and they tremble” at you. They may talk about “head faith versus heart faith”, or say that “real faith is obedient faith.”
And, yet, we know that LSers don’t keep God’s laws. They may say they are trying, but trying is a work.
 For as many as are of the works of the law are under the curse: for it is written, Cursed is every one that continueth not in all things which are written in the book of the law to do them.
 But that no man is justified by the law in the sight of God, it is evident: for, The just shall live by faith.
LS is the unsupportable belief that the PERFORMANCE of works, the PROMISE of works, or the EVIDENCE of works must accompany faith in Christ in order to establish, or provide evidence, that such faith has resulted in eternal life.
Lordship “salvation” is no salvation at all. It is belief in salvation by works. It is believing in vain.
For a message of hope that is not vain, click here: Eternal Life for You