The King is sending an Easter message about “care and friendship” ahead of his public appearance on Sunday.
Charles is to highlight the importance of friendship “especially in a time of need” in the wake of his and Princess Kate’s cancer diagnoses.
It comes before the King’s first official public outing since his cancer diagnosis on Sunday.
The King and Queen will attend this week’s Easter Sunday service at St George’s Chapel in Windsor.
The King is sending an Easter message in his absence from the Maundy service
PA
The pre-recorded audio message will be the King’s first public words since the Princess of Wales revealed her cancer diagnosis on Friday.
The message will be broadcast in his absence at the Royal Maundy service in Worcester Cathedral on Thursday.
Queen Camilla is set to make history as the first consort to lead the traditional Easter ceremony as the King continues his cancer treatment.
The King will comment on how Jesus was an “example of how we should serve and care for each other” and as a nation “we need and benefit greatly from those who extend the hand of friendship to us, especially in a time of need.”
Queen Camilla and King Charles will be attending this week's Easter Sunday serviceGettyAlthough the King does not directly mention his daughter-in-law, it sends a poignant message surrounding her recent health announcement.
The princess is already said to be “extremely moved” by the amount of public, worldwide support she received after her video message.
King Charles has also recorded a Bible reading for the Easter engagement along with his personal message.
The King is expected to describe the Maundy money recipients as “wonderful examples of such kindness” in “giving so much of their lives to the service of others in their communities.”
The Queen will hand out Maundy gifts at Worcester CathedralGettyCharles was pictured sitting at his desk in Buckingham Palace’s 18th century Room as he recorded his message.
On Thursday, the Queen will present purses of coins to 75 men and 75 women for the Ceremony of the Royal Maundy.
Maundy Thursday is an Easter celebration and marks the night of the Last Supper in the Bible.
The occasion marks the end of Lent on the Christian calendar and comes on the last Thursday before Easter.
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King Charles has recorded a bible reading and a personal message
GettyThe anti-monarchy group Republic is expected to protest outside the service on Thursday for the Queen’s visit.
Despite the King and the Princess of Wales’s cancer diagnosis, the group has said it will continue campaigning against the institution.
Graham Smith, the chief executive of the group said: “Unlike royalists, we don’t conflate the family with the institution. It’s the institution we’re protesting against this week.
“This is a campaign about principles, politics and reform.”