The dialogue is drawn from The Two Towers, "The Voice of Saruman." For Tallis.
“When last I visited you, you were the jailor of Mordor, and there I was to be sent.” Saruman controlled his temper as he heard Gandalf out. “Think well, Saruman. Will you not come down?”
“There are conditions, I presume?”
“You will first surrender to me the Key of Orthanc, and your staff.”
“If you wish to treat with me, while you have a chance, go away, and come back when you are sober! ... Good day!”
“Come back, Saruman!”
Never had he heard such a voice of command, not here within Middle Earth, not even in his communions with the Lord of Mordor. Saruman turned reluctantly, and quailed. Looking at his fellow Istar he saw not the Man’s seeming that Gandalf had worn for much of this last age of the Sun, but instead the royal might of the Maia that that seeming hid. Although Gandalf did not bother to part the grey cloak he wore over his white robes, there could be no question of the power he held being unveiled, the Light of his Being blazing forth as bright as Arien herself. And within Gandalf’s new staff was such potential! How Saruman hungered for it! He grasped his own staff to him, prepared to draw from it the power he needed to wrest that of his rival from him. But it answered him not!
Fool! Ah, Curumo, how little of you as you were is left, for you have spent it profligately over the years. Each time you have practiced cunning rather than charity, treachery rather than honoring your alliances, relied on craft rather than on honest dealings, you have lost a bit more of your true self. And what is left of you, I wonder?
Gandalf raised his staff slightly. “Saruman, your staff is broken!” And the ebon wood of Saruman’s staff burst into a thousand fragments, fragments that caught fire and burned swiftly to ash. Only he and Gandalf between them knew, however, that this act was but a show for the others, that there had been no power left within it for him to draw upon.
Saruman felt his heart twist within him, realizing he was now little better than those who followed in the train of Olórin.