17 But the soldiers who crowd around mock Him, and their Lord becomes a sport to them, and upon their Master they make jests. When they looked on Me, they shaked their heads. Yet the figure of kingly state appears; for though in mockery, yet they bend the knee. And the soldiers before they crucify Him, put on Him a purple robe, and set a crown on His head; for what though it be of thorns? Every king is proclaimed by soldiers; and Jesus also must in a figure be crowned by soldiers; so that for this cause the Scripture says in the Canticles, Go forth, O you daughters of Jerusalem, and look upon King Solomon in the crown wherewith His mother crowned Him. And the crown itself was a mystery; for it was a remission of sins, a release from the curse.
Source: Catechetical Lectures (New Advent)