“But the wisdom that comes from heaven is first of all pure; then peace-loving, considerate, submissive, full of mercy and good fruit, impartial and sincere. Peacemakers who sow in peace reap a harvest of righteousness.” James 3”17-18
“Wisdom from heaven” is a Gift from God that makes us alive in faith and guides us to live by His Word.
“First of all pure” indicates our hearts are purified by Christ and therefore unstained by the world.
“Then” good works can flow from a heart that has been purified by Christ. The traits listed enable us to build others up. All contrast with cursing and boasting.
“Impartial” … here is Luther’s commentary, “It is certain that no man who is busy with commandments or righteousness performs this true service. They cannot even comprehend it intellectually. For it is a teaching revealed from heaven which does not arise from the human heart or mind. The Holy Spirit must be the Teacher and Guide. Since He reaches men only through faith in Christ, whereas the work-righteous reject faith and retain the Law, it is impossible for them to perform this service. Therefore the Christian religion is easy, as I said, if you regard only the outward acts. But if you consider this spiritual service, it is most difficult, for you cannot perform this unless your heart is changed”.
“Harvest of righteousness” is a bounty of righteous actions. There is no limit to the benefits others receive from our righteous actions.
“Peace” is repeated for emphasis, and contrasts with the cursing, poisonous tongue.
There are only two ways to live … by the “wisdom” of the world or by God’s wisdom. James condemns the worldly pattern of selfishness, deception, hurtful words, and other evil behaviors. Christians, too, struggle with such sins and are even tempted to present themselves as holier than others. How different is the wisdom of God. He has purified us in Christ and freed us from the stain of the world. We now walk in the works He has prepared for us to.