First Saruman was shown that the power of his voice was waning. He cannot be both tyrant and counsellor. When the plot is ripe it remains no longer secret. Yet he fell into the trap, and tried to deal with his victims piece-meal, while others listened. Then I gave him a last choice and a fair one: to renounce both Mordor and his private schemes, and make amends by helping us in our need. He knows our need, none better. Great service he could have rendered. But he has chosen to withhold it, and keep the power of Orthanc. He will not serve, only command. He lives now in terror of the shadow of Mordor, and yet he still dreams of riding the storm. Unhappy fool! He will be devoured, if the power of the East stretches out its arms to Isengard. We cannot destroy Orthanc from without, but Sauron – who knows what he can do?’ ‘And what if Sauron does not conquer? What will you do to him?’ asked Pippin. ‘I? Nothing!’ said Gandalf. ‘I will do nothing to him. I do not wish for mastery. What will become of him? I cannot say.

J.R.R. Tolkien (2009-04-17). The Lord of the Rings (pp. 584-585). Harper Collins, Inc.. Kindle Edition.