Sen. John McCain (R-Ariz.) lost his battle at age 81 with glioblastoma, a deadly brain cancer, on Saturday.

As plans are being finalized to pay tribute to the senator in both his home state of Arizona and in the Capitol rotunda in Washington, D.C., his longtime aide Rick Davis read a statement from the senator on Monday morning, which included a stern rebuke of President Donald Trump. McCain did so as he cautioned that America is weakened “when we hide behind walls.”

McCain reportedly dictated the statement in the final days of his life.

Davis, before he began reading McCain’s letter, took a sip of bottled water and, obviously feeling very emotional, warned, “This will be somewhat difficult.”

McCain’s letter included poetic phrases about his love for America and his gratitude to his family and his nation — and his feeling that, even when ill, he was indeed the luckiest of men.

But wrapped inside his patriotic statement were stinging words of caution to all Americans.

“We weaken our greatness when we confuse our patriotism with tribal rivalries that have sown resentment and hatred and violence in all the corners of the globe,” McCain’s statement read.

“We weaken it when we hide behind walls, rather than tear them down, when we doubt the power of our ideals, rather than trust them to be the great force for change they have always been,” he continued.

“Like most people, I have regrets. But I would not trade a day of my life, in good or bad times, for the best day of anyone else’s.”

Related: McCain’s Confidential Request Made Public, Trump Banned from Funeral

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McCain also noted, “We are 325 million opinionated, vociferous individuals. We argue and compete and sometimes even vilify each other in our raucous public debates.”

Noting today’s political discord, he also advised Americans in his statement, “But we have always had so much more in common with each other than in disagreement. If only we remember that and give each other the benefit of the presumption that we all love our country, we will get through these challenging times. We will come through them stronger than before. We always do.”

“Americans never quit. We never surrender. We never hide from history. We make history.”

He concluded, “Do not despair of our present difficulties but believe always in the promise and greatness of America, because nothing is inevitable here. Americans never quit. We never surrender. We never hide from history. We make history.”

McCain’s final words came as Trump on Monday declined to answer reporters’ questions about his thoughts on the senator’s legacy.

Trump was also criticized for not issuing a formal proclamation in the wake of the senator’s death — as is traditional when a notable citizen dies.

The president instead issued a tweet offering prayers to the senator’s family.

Additionally, the flag at the White House was returned to full-staff on Monday after being at half-staff on Sunday.

Davis declined to answer any questions about the flag or about Trump’s response to McCain’s death.

“The entire focus of McCain family is on John McCain. There really is no room in the McCain family today to focus on anything but him,” Davis said.

Related: The Good, the Bad and the Ugly of John McCain

“I think any discussion of what any one individual has done or said, if you look at the gravity of all the reactions around the world — world leaders, our allies — it’s been immense,” he added. “They choose to focus on that.”

Check out the video of the McCain statement as read on Monday: