It is written in Proverbs: "He who digs a pit will fall into it; and when one starts a stone rolling it will roll back upon him" (Proverbs 26). So too Haman was forced to suffer the cross he had prepared for Mordecai.
We might, however, ask what it means that, as we have read, the cross itself was made fifty cubits high. For the Law had previously been given to the people on the fiftieth day after a lamb was sacrificed on Mount Sinai; and given that we said before that Haman signified the Jews themselves when they were rioting against Christ—who had been promised to them in the Law—and persecuting his Church, the Law itself, which had been given to them to safeguard their lives, became the cause of their deaths because with it they had snuffed out the name of Christ and tried mightily to kill those who professed him. In other words, those who wanted by means of the Law to oppress the guiltless unjustly received through it the verdict of a just judgment, about which we are told by Paul: "Whoever has sinned in the Law will be judged through the Law" (Romans 2).
Moreover, Harbona the eunuch, who handed over the actual cross that had been made, signifies the teachers of the Law who brought to light—by reading the Law itself—the deceit of the Jews and everything which they did contrary to the precepts of God. Hence because Moses foresaw in the spirit the rebels and apostates who would one day come to be, he predicted in his song in Deuteronomy everything that was going to happen to sinners. So too the Savior says to the Jews themselves in the Gospel: "Do not think that I am going to indict you before the Father—it is Moses, in whom you hope, who accuses you; for if you believed in Moses you would perhaps believe in me as well, for it is about me that he wrote. But if you do not believe what he wrote, then how will you believe my words (John 5)?"
We might, however, ask what it means that, as we have read, the cross itself was made fifty cubits high. For the Law had previously been given to the people on the fiftieth day after a lamb was sacrificed on Mount Sinai; and given that we said before that Haman signified the Jews themselves when they were rioting against Christ—who had been promised to them in the Law—and persecuting his Church, the Law itself, which had been given to them to safeguard their lives, became the cause of their deaths because with it they had snuffed out the name of Christ and tried mightily to kill those who professed him. In other words, those who wanted by means of the Law to oppress the guiltless unjustly received through it the verdict of a just judgment, about which we are told by Paul: "Whoever has sinned in the Law will be judged through the Law" (Romans 2).
Moreover, Harbona the eunuch, who handed over the actual cross that had been made, signifies the teachers of the Law who brought to light—by reading the Law itself—the deceit of the Jews and everything which they did contrary to the precepts of God. Hence because Moses foresaw in the spirit the rebels and apostates who would one day come to be, he predicted in his song in Deuteronomy everything that was going to happen to sinners. So too the Savior says to the Jews themselves in the Gospel: "Do not think that I am going to indict you before the Father—it is Moses, in whom you hope, who accuses you; for if you believed in Moses you would perhaps believe in me as well, for it is about me that he wrote. But if you do not believe what he wrote, then how will you believe my words (John 5)?"
Source: Commentary on Esther