Charles Ellicott Commentary 2 Samuel 16:6

"And he cast stones at David, and at all the servants of king David: and all the people and all the mighty men were on his right hand and on his left." — 2 Samuel 16:6 (ASV)

He cast stones. —The road appears to have led along the side of a narrow ravine, on the opposite side of which (see 2 Samuel 16:9, let me go over) Shimei kept along with the fugitives, out of reach, and yet easily heard, and able to annoy them with stones.