Who is wise and understanding among you? Let them show it by their good life, by deeds done in the humility that comes from wisdom.
Where do wisdom and understanding come from? Experience? Education? Psalm 111:10 and Proverbs 9:10 both tells us that the fear (reverence) of God is the beginning of wisdom and that knowledge of the Lord, and following His precepts, is the path to understanding.
James likewise treats wisdom (application) as inseparable from understanding (knowledge), at the same time challenging his readers, in his characteristic evidence-based style, to consider how we gauge wisdom. Jumping immediately to the answer, James adds that the proof of wisdom is found in our acts of service carried out with humility. He builds on this thought in subsequent verses, showing that there is no room for envy or selfish ambition in the wisdom of heaven.
The wise person, then, is the one who in reverence of God, puts his knowledge and understanding of the Lord into practice in his actions. The wise person does nothing out of vain conceit. Instead, he looks after the interests of others, imitating the humility of Christ, who took on the nature of a servant and humbled himself to death on a cross, for the sake of others (Philippians 2:3-8). This is the model of humility that displays true wisdom and understanding.