President Joe Biden quoted the late Queen Elizabeth II in a speech Sunday remembering the victims of the Sept. 11 terrorist attacks.

“Grief is the price we pay for love,” Biden said, referring to a message sent by the monarch, who died last week, after the attacks that killed almost 3,000 people.

“Many of us have experienced that grief, and you’ve all experienced it. And on this day, when the price feels so great, Jill and I are holding all of you close to our hearts,” Biden said, citing first lady Jill Biden, who was to speak Sunday at the Flight 93 crash site in Shanksville, Pa.

In his speech at the Pentagon commemorating the 21st anniversary of the deadly attacks, Biden repeatedly called for remembrance and unity.

“I hope we’ll remember that amidst those dark days, we dug deep, we cared for each other, and we came together,” Biden said of the national unity in the days after the 2001 attacks.

Biden framed the anniversary as a day of “renewal and resolve” for Americans’ devotion to both the United States itself and democratic principles overall.

“It’s not enough to stand up for democracy once a year,” he said.