Adam Clarke on James 4:10

Humble yourselves in the sight of the Lord - In Jam 4:7 they were exhorted to submit to God; here they are exhorted to humble themselves in his sight. Submission to God's authority will precede humiliation of soul, and genuine repentance is performed as in the sight of God; for when a sinner is truly awakened to a sense of his guilt and danger, he seems to see, whithersoever he turns, the face of a justly incensed God turned against him.

He shall lift you up - Mourners and penitents lay on the ground, and rolled themselves in the dust. When comforted and pardoned, they arose from the earth, shook themselves from the dust, and clothed themselves in their better garments. God promises to raise these from the dust, when sufficiently humbled.