The King has recorded a message for the Maundy Thursday service praising those who “extend the hand of friendship, especially in a time of need”.
The message will be played at the service at Worcester Cathedral.
The King, who is being treated for cancer, will not be attending and Queen Camilla will hand out the traditional “Maundy money” on his behalf.
The number of recipients matches the age of the monarch – so 75 men and women will receive this symbolic gift.
The King’s message, recorded in mid-March, will include a Bible reading and a call that as a nation: “We need and benefit greatly from those who extend the hand of friendship to us, especially in a time of need.”
Although not directly commenting on his own health – or the cancer diagnosis of the Princess of Wales – he will speak of the importance of those who care for others.
His message will say “we should serve and care for each other” and will repeat his Coronation promise “not to be served but to serve”.
The Maundy service, in which the monarch gives out gifts, is one of the oldest royal ceremonies, dating back at least as far as the 13th Century and the reign of King John, a monarch who is buried in this medieval cathedral.
Until James II in the 17th Century, the monarch also used to wash the feet of the poor, in an echo of Jesus washing the feet of the apostles at the Last Supper.
Now the ceremony involves giving purses of coins to older people, 75 men and 75 women, who have been involved in helping the church and the local community.
This year’s recipients will receive £5 coins with the image of a Tudor dragon, a 50p marking the The Royal National Lifeboat Institution’s 200th anniversary and specially minted silver Maundy coins.
The King’s message will praise those getting the Maundy money as “wonderful examples of such kindness”.
This is another engagement in which Queen Camilla has appeared on behalf of the King, while he continues with the cancer treatment that began last month.
He has not attended big public events with large crowds, but he will be at the Easter church service on Sunday morning at St George’s Chapel in Windsor.
It will be a smaller event this Easter, with the Prince and Princess of Wales and their children not attending, as Catherine continues her recovery.
The King had sent a video message to the annual Commonwealth service earlier this month, but it is understood that Worcester Cathedral did not have the video facilities, so an audio message will be played instead.
The anti-monarchy group Republic issued a statement ahead of the service saying the monarchy is “bad for Britain’s democracy” and the Queen’s visit to Worcester will be a sign of “how out of touch the monarchy is with the values of most of us”.