“What doth it profit, my brethren, though a man say he hath faith, and have not works? can faith save him? If a brother or sister be naked, and destitute of daily food, And one of you say unto them, Depart in peace, be ye warmed and filled; notwithstanding ye give them not those things which are needful to the body; what doth it profit? Even so faith, if it hath not works, is dead, being alone. Yea, a man may say, Thou hast faith, and I have works: shew me thy faith without thy works, and I will shew thee my faith by my works. Thou believest that there is one God; thou doest well: the devils also believe, and tremble. But wilt thou know, O vain man, that faith without works is dead? Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar? Seest thou how faith wrought with his works, and by works was faith made perfect? And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness: and he was called the Friend of God. Ye see then how that by works a man is justified, and not by faith only. Likewise also was not Rahab the harlot justified by works, when she had received the messengers, and had sent them out another way? For as the body without the spirit is dead, so faith without works is dead also.” (James 2:14-26, KJV)
We see Christians often take this passage as a proof-text against the doctrine of faith-only salvation. However, while there is a means of making such a case from this passage, that is not the purpose for which the writer includes this section.
You see, James is writing to Christians, to those who are already members of the body of Christ. So take a moment and consider the exact question that James is asking. If God asked you to prove your faith by your deeds right now, could you do it? As a Christian, you claim belief in God, faith in his word, and dedication to his cause: can you prove it? Do the things found in your life indicate in any way that you are different from the rest of the world, or that you love your brethren like your own family? Your words are not enough, a man requires more to be justified before God than words from a pew. What does your life say? Christians, how would you answer? Is your faith alive or dead?
As a final note, there is a case that can be made from this passage against faith only and it is this: if a Christian cannot be justified before God with only the words of his faith, how can a non-Christian?