Man could not, of himself, atone for sin. Only God, who had never sinned, could make fitting satisfaction for it. Therefore He, in His infinite mercy, wisdom, and power, willed, by becoming man, to pay the debt which man owed, and was unable to pay.
Man owed satisfaction, and God-made Man alone had power to make that satisfaction, not indeed for Himself, but for the whole human race. In this fact is revealed the fitness of His Incarnation, wherein He has united the Divine to the Human nature. In this mystery we behold His power, His wisdom, and the goodness whereby He has wholly given Himself to the human race, to embrace it, and to draw it to His love. But, above all His other attributes, His mercy is made manifest; for it has led Him to be crucified for love of us. His justice also is seen; for He has Himself made satisfaction for original sin. Hence, while His mercy should inspire repentant sinners with the surest hope, His justice should cause the impenitent to tremble. This is the reason why, since the coming of Christ into the world, so many men have been drawn from sin to holiness of life.
When we consider these mercies, and the innumerable other benefits conferred by Christ upon human nature, we discover depths of wisdom which are unfathomable by the intellect of man, and which, for this very reason, are accounted folly by the world. We see, moreover, how fitting it was that Christ should suffer for the guilt of mankind.
But since He came, not merely to suffer for man, but likewise to set him an example of righteous living, it behoved Him to choose a most bitter and disgraceful death; thus teaching us that neither shame, nor suffering, should force us to betray the cause of truth and justice.
Time forbids me to enlarge upon the other reasons which caused our Saviour to choose His terrible mode of death. I will only add, that His cross has been, to them that love Him, a fount of sweetness and of light, known only to those who have experienced it.
-Girolamo Savonarola, Triumph of the Cross.