The Archbishop of Canterbury said he hoped the UK would pray for the Queen during Prince Philip's funeral.
Justin Welby said the Queen will behave with "the extraordinary dignity and extraordinary courage that she always does."
But he said it must be a very profound thing to say goodbye to someone she was married to for 73 years, and asked for the nation to offer condolences and sympathise in their hearts.
The archbishop, who will lead the service alongside the dean of Windsor, said it would be wrong to judge how the 94-year-old monarch was feeling from her appearance at the ceremony.
Speaking to the BBC, Justin Welby said: "We really have to avoid judging from anything external.
"She is the Queen. She will behave with the extraordinary dignity and extraordinary courage that she always does.
"And at the same time she is saying farewell to someone to whom she was married for 73 years.
"I think that must be a very, very profound thing in anybody's life and I hope the whole nation, if they believe in that, they pray for her, and if they don't, they sympathise in their hearts, offer their condolences to her and they hope for her to find strength in what must be an anguished moment."
The Duke of Edinburgh, who had been married to the Queen since 1947, died on April 9 at Windsor Castle aged 99, leaving a "huge void" in her life.
On Saturday, a ceremonial royal funeral will be held at the castle's St George's Chapel, a scaled-down ceremony because of coronavirus restrictions although there will be some traditional grandeur.