After leaving Verona, Cardinal Borromeo continued his journey to Trent, where, having paid his respects to the two Princesses according to the intentions of His Holiness, he accompanied them from there, one to Ferrara, and the other as far as Fiorenzole in Tuscany.
It was there that a courier came to bring him the news that the Pope was dangerously ill. The Cardinal immediately took post-horses and made great haste to Rome. The first thing he did upon his arrival was to learn from the doctors the state of His Holiness's illness and the truth of what they thought of it.
Having learned from them that all hope was lost, he immediately approached the sick man's bed; and commanding his own grief, he made the Holy Father understand that he must profit from every moment, since the hour to pass to another life had come for him. He had the fortitude, while presenting him with the image of the Crucifix, to speak to him in these terms:
"Most Holy Father, all your desires and all your thoughts must now turn only towards Heaven. Behold this crucified Jesus, the sole foundation of all our hopes, He is our resurrection and our life, He is our Mediator and our Advocate.
He is the victim and the sacrifice offered for our sins, He rejects none of those who, touched by a sincere repentance for having offended Him, place all their trust in Him, acknowledging Him as true God and true man.
He is Goodness and Mercy itself. This Mercy always allows itself to be moved by the tears of Sinners, and grants grace to those who ask for it in a true spirit of penance, with a heart perfectly contrite and humbled."
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After this short exhortation, the Cardinal added that he had a favor to ask of His Holiness, and that he asked it as one of the greatest he had ever received from him. The Pope signifying his consent to all that would be required of him, the Cardinal resumed, saying that since there was no longer any hope of life for him, he begged him most earnestly to apply himself, during the little time that remained, only to the thought of his salvation.
To gather all the knowledge and strength he had to prepare himself, with God's help, to appear before Him. The Pope listened very attentively to all these words and appeared to receive them with great consolation. Saint Charles, having then ordered all his people to unite their prayers with those already being offered publicly in all the churches of Rome, forbade anyone to speak to the Pope of anything else; he himself remained in prayer beside him until he had breathed his last.
He had the strength to administer with his own hands the Holy Viaticum and Extreme Unction and did not cease to dispose him to die well through all the pious practices that Religion prescribes, or that his charity inspired in him.
Pius IV, aged sixty-six years and eight months, after six years of Pontificate, died while pronouncing with great sentiments of piety these words of the holy old man Simeon:
"Now, Lord, you may let your servant die in peace, according to your word."
This death occurred on the tenth day of December 1565.
However hard and terrible this blow was, Saint Charles bore it with great strength of spirit and perfect tranquility, because one of his great virtues was an entire submission to the orders of God, whose will was the ordinary rule of all the movements of his heart, and of all the actions of his life.
It is true that if the loss the Saintly Cardinal had just suffered was great, it was not in one sense entirely irreparable: he could well flatter himself with always enjoying the same authority and the same credit with the Successor of Pius IV.
Source: The Life and Spirit of Saint Charles Borromeo Cardinal & Archbishop of Milan – 1761