“Since when has the Lord of Gondor been answerable to thee?” said Denethor. “Or may I not command my own servants?”
“You may,” said Gandalf. “But others may contest your will, when it is turned to madness and evil.” – The Lord of the Rings: The Return of the King, Chapter Seven: The Pyre of Denethor by J. R. R. Tolkien
“He will not wake again,” said Denethor. “Battle is vain. Why should we wish to live longer? Why should we not go to death side by side?”
“Authority is not given to you, Steward of Gondor, to order the hour of your death,” answered Gandalf. “And only the heathen kings, under the domination of the Dark Power, did thus, slaying themselves in pride and despair, murdering their kin to ease their own death.”
Denethor and Gandalf in Chapter Seven of The Lord of the Rings: The Return of the King
“What then would you have,” said Gandalf, “if your will could have its way?”
“I would have things as they were in all the days of my life,” answered Denethor, “and in the days of my longfathers before me: to be the Lord of this City in peace, and leave my chair to a son after me, who would be his own master and no wizard’s pupil. But if doom denies this to me, then I will have naught: neither life diminished, nor love halved, nor honor abated.”
“To me it would not seem that a Steward who faithfully surrenders his charge is diminished in love or in honor,” said Gandalf. “And at the least you shall not rob your son of his choice while his death is still in doubt.”
Denethor and Gandalf in Chapter Seven of The Lord of the Rings: The Return of the King
Thoughts on the Edge of Forever 