James 2:10 For whosoever shall keep the whole law, and yet offend in one point, he is guilty of all.
11 For he that said, Do not commit adultery, said also, Do not kill. Now if thou commit no adultery, yet if thou kill, thou art become a transgressor of the law.
12 So speak ye, and so do, as they that shall be judged by the law of liberty.
13 For he shall have judgment without mercy, that hath shewed no mercy; and mercy rejoiceth against judgment.
This is speaking to those specifically who have not accepted the sacrifice that Jesus made as being sufficient for all sin, and are trying to keep the Mosaic law. The keeping of the law saves no one, because they cannot keep it in its entirety. The forgiveness through the blood of the Lord Jesus Christ saves you. James is trying to show, in this, that by the keeping of the law, no man is saved. The keepers of the law are not Christians, because they have not accepted the full pardon through the shed blood of Jesus for their sins. The law of liberty in Jesus Christ is what Christians are under. We are not perfect, just forgiven. A person who shows no mercy and compassion for people in need demonstrates that he has never responded to the great mercy of God, and as an unredeemed person will receive only strict, unrelieved judgment in eternal hell. This is so similar to what the Lord Jesus taught. Forgive, and you shall be forgiven. If you will not forgive, then you shall not be forgiven.