Members of the congregation who will be attending the funeral of Queen Elizabeth II have begun arriving at Westminster Abbey, three hours before it begins at 6 a.m. ET.

An estimated 2,000 people will be in attendance, including a number of foreign leaders and dignitaries.

The Archbishop of Canterbury tweeted earlier this morning, saying: "Let us pray for the Royal Family as they gather today to commend Her Majesty Queen Elizabeth II into the hands of our loving and faithful God. We come together to give thanks for a long life, lived in service to her people and her Saviour, Jesus Christ."

The royal family has released a new photo of Queen Elizabeth II ahead of her funeral on Monday.

"The photo was taken to mark Her Majesty’s Platinum Jubilee -- the first British Monarch to reach this milestone," the royal family wrote on Twitter. "Tomorrow, millions will come together to commemorate her remarkable life."

The order of service has been released for Queen Elizabeth II's state funeral Monday, including who will walk in the procession behind the queen's coffin.

According to the order, Prince George and Princess Charlotte are expected to walk behind their parents, William, Prince of Wales, and Catherine, Princess of Wales, respectively.

"Over the last ten days, my wife and I have been so deeply touched by the many messages of condolence and support we have received from this country and across the world," King Charles said in the written message issued by Buckingham Palace on Sunday.

"In London, Edinburgh, Hillsborough and Cardiff we were moved beyond measure by everyone who took the trouble to come and pay their respects to the lifelong service of my dear mother, The late Queen," he said. "As we all prepare to say our last farewell, I wanted simply to take this opportunity to say thank you to all those countless people who have been such a support and comfort to my Family and myself in this time of grief."

-ABC News' Zoe Magee