John Wesley on 2 Samuel 18:9

The servants of David - Who, according to David's command, spared him, and gave him an opportunity to escape. His head - In which probably he was entangled by the hair of the head, which being very long and thick, might easily catch hold of a bough, especially when the great God directed it. Either he wore no helmet, or he had thrown it away as well as his other arms, to hasten his flight. Thus the matter of his pride was the instrument of his ruin.