Then said Zeresh his wife and all his friends unto him, Let a gallows be made of fifty cubits high, and to morrow speak thou unto the king that Mordecai may be hanged thereon: then go thou in merrily with the king unto the banquet. And the thing pleased Haman; and he caused the gallows to be made. Let a gallows be made of fifty cubits high - The word עץ ets, which we translate gallows, signifies simply wood, a tree, or pole; and this was to be seventy-five feet high, that he might suffer the greater ignominy, and be a more public spectacle. I believe impaling is here also meant. See the note, Esther 2:23 (note).
In former times the Jews were accustomed to burn Haman in effigy; and with him a wooden cross, which they pretended to be in memory of that which he had erected for the suspension of Mordecai; but which was, in fact, to deride the Christian religion. The emperors, Justinian and Theodosius, abolished it by their edicts; and the practice has ceased from that time, though the principle from which it sprang still exists, with the same virulence against Christianity and its glorious Author.
Commentary on the Bible, by Adam Clarke [1831].