These words were spoken in contemptuous imitation of the words addressed to a Roman Emperor, on his assuming imperial power: “Hail, Emperor!” It was as much as saying, “Thou a King indeed! Thou and Thy kingdom are alike contemptible.
” (Bp. Ryle.)
It was the kingdom of the Jews itself that the soldiers laughed at. They regarded Jesus as the representative of the Messianic hope of the Jews. They would turn to ridicule these royal hopes, which were known widely in the heathen world, more especially as they aspired to the dominion of the whole earth. (Hengstenburg.)
