There came from France in those days Benvenuto Cellini, who had served King Francis in the matter of goldsmith's work, of which he was the most famous master of his day; and he had also executed some castings in bronze for that King. Benvenuto was introduced to Duke Cosimo, who, desiring to adorn the city, showed also to him much favour and affection, and commissioned him to make a statue of bronze about five braccia high, of a nude Perseus standing over a nude woman representing Medusa, whose head he had cut off; which work was to be placed under one of the arches of the Loggia in the Piazza. While he was executing the Perseus, Benvenuto also did other things for the Duke. Now, even as it happens that the potter is always the jealous enemy of the potter, and the sculptor of the sculptor, Baccio was not able to endure the various favours shown to Benvenuto. It appeared to him a strange thing, also, that Benvenuto should have thus changed in a moment from a goldsmith into a sculptor, nor was he able to grasp in his mind how a man who was used to making medals and little things, could now execute colossal figures and giants. Baccio could not conceal his thoughts, but expressed them freely, and he found a man able to answer him; for, Baccio saying many of his biting words to Benvenuto in the presence of the Duke, Benvenuto, who was no less proud than himself, took pains to be even with him. And thus, arguing often on the matters of art and their own works, and pointing out each other's defects, they would utter the most slanderous words of one another in the presence of the Duke, who, because he took pleasure in this and recognized true genius and acuteness in their biting phrases, had given them full liberty and licence to say whatever they pleased about one another before him, provided that they did not remember their quarrel elsewhere.
This rivalry, or rather, enmity, was the reason that Baccio pressed forward his statue of God the Father; but he was no longer receiving from the Duke those favours to which he had been accustomed, and he consoled himself for this by paying court and doing service to the Duchess. One day, among others, that they were railing at one another as usual and laying bare many of each others' actions, Benvenuto, glaring at Baccio and threatening him, said: "Prepare yourself for another world, Baccio, for I mean to send you out of this one." And Baccio answered: "Let me know a day beforehand, so that I may confess and make my will, and may not die like the sort of beast that you are." By reason of which the Duke, who for many months had found amusement in their quarrels, bade them be silent, fearing some evil ending, and caused them to make a portrait-bust of himself from the girdle upwards, both to be cast in bronze, to the end that he who should succeed best should carry off the honours.